0001193125-26-285725 | 11-K | XBRL Viewer

EBP, Schedule of Asset Held for Investment [Line Items]

Schedule of Assets (Held at End of Year)

KIRBY 401(k) PLAN

EIN 74-1884980, Plan #004

Schedule H, Part IV, Line 4i – Schedule of Assets (Held at End of Year)

(Modified Cash Basis)

December 31, 2025


Identity of issue, borrower, lessor, or similar party	Description of asset	Current value
Common trust funds:
T. Rowe Price	T. Rowe Price retirement 2010A TR	$	1,498,140
T. Rowe Price	T. Rowe Price retirement 2015A TR		1,770,041
T. Rowe Price	T. Rowe Price retirement 2020A TR		14,024,832
T. Rowe Price	T. Rowe Price retirement 2025A TR		8,296,900
T. Rowe Price	T. Rowe Price retirement 2030A TR		19,522,473
T. Rowe Price	T. Rowe Price retirement 2035A TR		10,656,944
T. Rowe Price	T. Rowe Price retirement 2040A TR		16,769,470
T. Rowe Price	T. Rowe Price retirement 2045A TR		5,466,494
T. Rowe Price	T. Rowe Price retirement 2050A TR		4,184,855
T. Rowe Price	T. Rowe Price retirement 2055A TR		2,756,961
T. Rowe Price	T. Rowe Price retirement 2060A TR		409,439
T. Rowe Price	T. Rowe Price retirement 2065A TR		280,977
Franklin Templeton	Putnam Large Cap Value Trust CL1		38,099,106
Northern Trust	Northern Trust MSCI ACWI EX US Index TR 3		79,543,793
Invesco	Invesco Stable Value Retirement Fund CL1		97,253,884
BlackRock	BlackRock Russell 2000 Fund		40,256,378
Northern Trust	Northern Trust Aggregate Bond Index DC NL Tier 3		65,602,299
Northern Trust	Northern Trust S&P 500 Tier 3		175,687,980
Total common trust funds			582,080,966
Mutual Funds:
American Funds	American Bond Fund of America Class R-6		20,175,898
Prudential Jennison	Prudential Jennison Large Cap Growth Fund		93,129,326
Fidelity	Fidelity Mid Cap Index		42,611,039
Dimensional Fund Advisors	DFA Real Estate Securities Portfolio Institutional Class		12,999,376
Northern Trust	Active Multi-Manager Emerging Markets Equity Fund		10,904,155
PIMCO	PIMCO Rae US Small Fund Institutional Class		23,518,042
Harbor	Harbor International Fund		51,132,452
American Century	American Century Small Cap GR R6		21,645,481
Blackrock	Blackrock Global Allocation Fund		3,951,024
Total mutual funds			280,066,793
Common stock:
*Kirby Corporation	Common stock		53,677,515
*Participant loans	Interest rates ranging from 4.0% to 10.3% and maturity dates from January 7, 2026 to March 15, 2039		28,882,175
Total assets (held at end of year)		$	944,707,449

* Parties in interest to the Plan

See accompanying report of independent registered public accounting firm.

Statements of Changes in Net Assets Available for Benefits - EBP 004 - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Additions to net assets attributed to:
Contributions from participants	$ 32,686,608	$ 30,123,133
Contributions from employer, net of forfeitures	33,047,003	31,491,168
Rollover contributions	1,485,550	1,816,119
Dividend and other income	19,428,381	19,811,367
Interest income from participants' notes receivable	2,311,076	2,006,747
Net appreciation in fair value of investments	100,133,733	85,706,011
Total additions, net	189,092,351	170,954,545
Deductions from net assets attributed to:
Benefits paid to participants	93,669,827	97,425,381
Investment counselor fees and other	566,434	541,791
Total deductions	94,236,261	97,967,172
Net increase	94,856,090	72,987,373
Net assets available for benefits, beginning of year	850,124,257	777,136,884
Net assets available for benefits, end of year	$ 944,980,347	$ 850,124,257

Federal Income Tax Status	12 Months Ended
Dec. 31, 2025
EBP 004
EBP, Tax Status [Line Items]
Federal Income Tax Status	(7) Federal Income Tax Status The IRS has determined and informed the Company by a letter dated August 25, 2017, that the Plan and related trust are designed in accordance with applicable sections of the Internal Revenue Code (“IRC”). Although the Plan has been amended since receiving the determination letter, Plan management believes that the Plan is designed, and is currently being operated, in compliance with the applicable requirements of the IRC and, therefore, believes that the Plan is qualified, and the related trust is tax-exempt. The Plan is currently open to audit under the statute of limitations by the IRS for the 2022 through 2024 tax years. The Plan has not recognized any assets or liabilities related to uncertain tax positions as of December 31, 2025 and 2024.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2025

EBP, Investment, Fair Value and NAV [Line Items]

Schedule of Investments Measured at Fair Value on a Recurring Basis

The following tables summarize the Plan’s investment assets measured at fair value on a recurring basis at December 31, 2025 and 2024:


	December 31, 2025
	Level 1		Total Fair Value
Mutual funds	$	280,066,793	$	280,066,793
Company common stock		53,677,515		53,677,515
Total assets in the fair value hierarchy	$	333,744,308		333,744,308
Common trust funds				582,080,966
Investments at fair value			$	915,825,274


	December 31, 2024
	Level 1		Total Fair Value
Mutual funds	$	250,926,227	$	250,926,227
Company common stock		53,035,000		53,035,000
Total assets in the fair value hierarchy	$	303,961,227		303,961,227
Common trust funds				518,596,463
Investments at fair value			$	822,557,690

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Tabular disclosure of fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).

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Statements of Net Assets Available for Benefits - EBP 004 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Assets:
Investments, at fair value	$ 915,825,274	$ 822,557,690
Notes receivable from participants	28,882,175	27,510,891
Other receivables	272,898	55,676
Total assets	944,980,347	850,124,257
Net assets available for benefits	$ 944,980,347	$ 850,124,257

Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria.

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Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances.

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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-03(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

EBP, Schedule of Asset Held for Investment [Line Items]

Schedule of Assets (Held at End of Year) (Details) - EBP 004

12 Months Ended

Dec. 31, 2025

USD ($)

EBP, Plan Number

004

Entity Tax Identification Number

74-1884980

EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution

$ 28,882,175

^[1]

EBP, Asset Held for Investment, Total

$ 944,707,449

EBP, Asset Held for Investment, Participant Loan, Maturity Date

Mar. 15, 2039

^[1]

Investment, Identifier [Axis]: Common Trust Funds

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 582,080,966

Investment, Identifier [Axis]: Common Trust Funds BlackRock Russell 2000 Fund

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

BlackRock [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 40,256,378

Investment, Identifier [Axis]: Common Trust Funds Franklin Templeton Putnam Large Cap Value Trust CL1

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Franklin Templeton [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 38,099,106

Investment, Identifier [Axis]: Common Trust Funds Invesco Stable Value Retirement Fund CL1

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Invesco [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 97,253,884

Investment, Identifier [Axis]: Common Trust Funds Northern Trust Aggregate Bond Index DC NL Tier 3

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Northern Trust [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 65,602,299

Investment, Identifier [Axis]: Common Trust Funds Northern Trust MSCI ACWI EX US Index TR 3

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Northern Trust [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 79,543,793

Investment, Identifier [Axis]: Common Trust Funds Northern Trust S&P 500 Tier 3

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Northern Trust [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 175,687,980

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2010A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 1,498,140

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2015A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 1,770,041

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2020A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 14,024,832

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2025A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 8,296,900

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2030A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 19,522,473

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2035A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 10,656,944

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2040A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 16,769,470

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2045A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 5,466,494

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2050A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 4,184,855

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2055A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 2,756,961

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2060A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 409,439

Investment, Identifier [Axis]: Common Trust Funds T. Rowe Price retirement 2065A TR

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

T. Rowe Price [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Common Collective Trust [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 280,977

Investment, Identifier [Axis]: Common stock Kirby Corporation Common stock

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Kirby Corporation Common stock [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

EBP, Employer, Common Stock [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Party-in-Interest [true false]

true

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 53,677,515

^[1]

Investment, Identifier [Axis]: Mutual Funds

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 280,066,793

Investment, Identifier [Axis]: Mutual Funds American Century Small Cap GR R6

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

American Century [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 21,645,481

Investment, Identifier [Axis]: Mutual Funds American Funds American Bond Fund of America Class R-6

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

American Funds [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 20,175,898

Investment, Identifier [Axis]: Mutual Funds Blackrock Global Allocation Fund

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

BlackRock [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 3,951,024

Investment, Identifier [Axis]: Mutual Funds Dimensional Fund Advisors DFA Real Estate Securities Portfolio Institutional Class

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Dimensional Fund Advisors [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 12,999,376

Investment, Identifier [Axis]: Mutual Funds Fidelity Mid Cap Index

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Fidelity [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 42,611,039

Investment, Identifier [Axis]: Mutual Funds Harbor International Fund

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Harbor [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 51,132,452

Investment, Identifier [Axis]: Mutual Funds Northern Trust Active Multi-Manager Emerging Markets Equity Fund

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Northern Trust [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 10,904,155

Investment, Identifier [Axis]: Mutual Funds PIMCO Rae US Small Fund Institutional Class

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

PIMCO [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 23,518,042

Investment, Identifier [Axis]: Mutual Funds Prudential Jennison Large Cap Growth Fund

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Investment, Issuer Name [Extensible Enumeration]

Prudential Jennison [Member]

EBP, Investment, Current Value, Type [Extensible Enumeration]

Mutual Fund [Member]

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]

us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember

EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value

$ 93,129,326

Minimum

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Asset Held for Investment, Participant Loan, Interest Rate

4.00%

^[1]

EBP, Asset Held for Investment, Participant Loan, Maturity Date

Jan. 07, 2026

Maximum

EBP, Schedule of Asset Held for Investment [Line Items]

EBP, Asset Held for Investment, Participant Loan, Interest Rate

10.30%

^[1]

EBP, Asset Held for Investment, Participant Loan, Maturity Date

Mar. 15, 2039

[1]	Parties in interest to the Plan

Description of Plan	12 Months Ended
Description of Plan	Dec. 31, 2025
EBP 004
EBP, Description of Plan [Line Items]
Description of Plan	(1) Description of Plan (a) General The Kirby 401(k) Plan (as amended and restated, the “Plan”) is a defined contribution 401(k) plan for the benefit of employees of Kirby Corporation (the “Company”) and certain subsidiaries. Employees covered by collective bargaining agreements, the terms of which do not provide for participation in the Plan, are not eligible. The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”). Further information relating to the Plan’s provisions is available in the Plan documents. (b) Administration of the Plan The general administration of the Plan is the responsibility of the Company (the “Plan Administrator”), and it has appointed the Kirby Corporation Administrative Committee to manage the Plan. The Plan Administrator has broad powers regarding the operation and administration of the Plan and receives no compensation for service to the Plan. Bank of America, N.A. (“Bank of America”) is the trustee of the Plan. (c) Contributions Each employee is eligible to join the Plan as of the first pay period following completion of three months of service and the attainment of age 18 unless specified otherwise by a collective bargaining agreement. The Plan allows Non-Highly Compensated Employees, as defined by the Internal Revenue Service (“IRS”), to contribute up to 50% of considered compensation, as defined by the Plan and Highly Compensated Employees to contribute up to 17% of considered compensation. Employee contributions to the Plan up to 50% of considered compensation are allowed under certain collective bargaining agreements. Participants age 50 or older during the Plan year may also elect to make a “catch‑up” contribution, subject to certain IRS limits ($7,500 in both 2025 and 2024, and a higher catch-up contribution of $11,250 for employees aged 60 through 63 in 2025). The Plan allows participants to designate their contributions as either pretax contributions or Roth (after-tax) contributions. The Company contributes matching employer contributions equal to 100% of the employee’s contribution, up to 3% of the employee’s considered compensation. Each participant directs his or her contributions and the Company’s matching contributions between the investment funds offered by the Plan, including Company common stock. Vessel based employees of Kirby Offshore Marine, LLC (“KOM”) whose employment is covered by collective bargaining agreements receive a non-discretionary employer match and may receive a discretionary employer contribution based on the terms of the applicable collective bargaining agreement. The Plan allows the employer, at its discretion, to make an additional employer discretionary contribution for eligible employees equal to 5% of the employees’ considered compensation. Eligible employees include employees of United Holdings, LLC (“United”), Stewart & Stevenson LLC (“S&S”), certain vessel personnel and shore based tankermen who are employees of Kirby Inland Marine, LP (“KIM”), and employees of KOM assigned the classification of Vessel Employee as determined by the Company. The Company made discretionary contributions of $17,629,538 and $17,100,956 to the Plan for eligible United, S&S, KIM, and KOM employees for the 2025 and 2024 Plan years, respectively. The Plan also allows the employer, at its discretion, to make a Profit Sharing contribution to eligible employees who are not covered under a collective bargaining agreement, the Company’s pension plans, or eligible to receive employer discretionary contributions as defined by the Plan. Under the provisions of the Plan, the employer (the Company or a participating company within the controlled group of the Company), may contribute, as a Profit Sharing Contribution, an amount, if any, as it shall deem appropriate, but the aggregate of such contributions shall not, with respect to either the Marine Group or the Diesel Group, as defined by the Plan, exceed (a) the lesser of (i) 12% of the total compensation paid or accrued to all eligible participants, as defined by the Plan, or (ii) the profit-based limit; in which the formula is defined by the Plan; or (b) such other amount as the Compensation Committee of the Board of Directors of the Company may determine at its sole discretion. On July 1, 2025, the Company made a Profit Sharing contribution of $4,496,498 to the Plan for the 2025 Plan year. On July 1, 2024, the Company made a Profit Sharing contribution of $4,260,826 to the Plan for the 2024 Plan year. The Plan allows the use of forfeited amounts to offset future employer matching contributions. Forfeitures from non-vested accounts of $2,173,357 and $1,992,488 were used to reduce the Plan’s matching contributions in 2025 and 2024, respectively. All employees hired or rehired are automatically enrolled at a 3% pretax contribution rate, unless otherwise elected by the participant. In addition, participants may contribute amounts representing rollovers from other qualified plans or from an individual retirement arrangement. (d) Benefits Benefit payments are made to participants upon retirement or termination of employment (or to the beneficiary in the event of death) and are in the form of lump sum or installment distribution payments. A participant may request a loan for up to the lesser of 50% of the participant’s vested interest or $50,000, less the participant’s highest outstanding loan balance during the preceding 12 months. Loans typically bear interest at prime rate plus 1%. Interest rates ranged from 4.0% to 10.3% at December 31, 2025. Loans outstanding at December 31, 2025 mature from January 7, 2026 through March 15, 2039. Loans outstanding upon a participant’s termination of employment are considered deemed distributions if not repaid and are deducted from the participant’s account balance prior to distribution. These amounts are taxed to the participant in the year of the participant’s termination. Active participants who qualify for an in-service withdrawal after attaining 59½ years of age may be paid their benefits in a single sum cash payment or rollover as soon as administratively possible. A Profit Sharing participant could, upon resignation from or discharge by the employer, withdraw the vested portion of the account relating to employer contributions. Distributions of the account relating to employer contributions could be paid as periodic payments or lump sum payments. Participants who reached the age of 55 and had completed six full years of vesting service were entitled to withdraw all vested amounts from his or her Profit Sharing account. Profit Sharing accounts are not available for a loan. The Plan requires automatic distribution of participant accounts upon termination without the participant’s consent of amounts less than $5,000 and greater than $1,000. If the participant does not elect to have the amount paid directly to an eligible retirement plan or receive a distribution directly, then the Plan will pay the distribution to an individual retirement plan designated by the Plan Administrator. Amounts less than $1,000 are paid directly to participants upon termination. (e) Vesting Participants are 100% vested in their participant contributions and rollovers, if any. Employer contributions are subject to a six-year vesting schedule. The vesting schedule of employer contributions for employees covered by collective bargaining agreements are specified by those particular agreements. Forfeitures in the amount of $365,520 and $192,586 as of December 31, 2025 and 2024, respectively, were available to offset future employer contributions or plan administrative expenses at the discretion of the Company. (f) Plan Termination Although it has not expressed any intent to do so, the Company has the right under the Plan to terminate the Plan subject to the provisions of ERISA. In the event of termination, the amounts credited to the accounts of participants will be distributed to the participants after payment of expenses for distribution and liquidation. (g) Participant Accounts Under the Plan, each participant’s account is credited with the participant’s contribution, the Company’s matching contribution, the Company's discretionary contribution, the Company's Profit Sharing contribution and an allocation of investment income (loss), net of administrative expenses. Investment income (loss) is allocated daily to participants. The benefit to which a participant is entitled is the benefit that can be provided from the participant’s vested account. (h) Administrative Expenses All administrative expenses, unless paid by the Company at its discretion, are paid by the Plan.

Schedule of Assets (Held at End of Year) (Tables)

12 Months Ended

Dec. 31, 2025

EBP, Schedule of Asset Held for Investment [Line Items]

Schedule of Assets


Identity of issue, borrower, lessor, or similar party	Description of asset	Current value
Common trust funds:
T. Rowe Price	T. Rowe Price retirement 2010A TR	$	1,498,140
T. Rowe Price	T. Rowe Price retirement 2015A TR		1,770,041
T. Rowe Price	T. Rowe Price retirement 2020A TR		14,024,832
T. Rowe Price	T. Rowe Price retirement 2025A TR		8,296,900
T. Rowe Price	T. Rowe Price retirement 2030A TR		19,522,473
T. Rowe Price	T. Rowe Price retirement 2035A TR		10,656,944
T. Rowe Price	T. Rowe Price retirement 2040A TR		16,769,470
T. Rowe Price	T. Rowe Price retirement 2045A TR		5,466,494
T. Rowe Price	T. Rowe Price retirement 2050A TR		4,184,855
T. Rowe Price	T. Rowe Price retirement 2055A TR		2,756,961
T. Rowe Price	T. Rowe Price retirement 2060A TR		409,439
T. Rowe Price	T. Rowe Price retirement 2065A TR		280,977
Franklin Templeton	Putnam Large Cap Value Trust CL1		38,099,106
Northern Trust	Northern Trust MSCI ACWI EX US Index TR 3		79,543,793
Invesco	Invesco Stable Value Retirement Fund CL1		97,253,884
BlackRock	BlackRock Russell 2000 Fund		40,256,378
Northern Trust	Northern Trust Aggregate Bond Index DC NL Tier 3		65,602,299
Northern Trust	Northern Trust S&P 500 Tier 3		175,687,980
Total common trust funds			582,080,966
Mutual Funds:
American Funds	American Bond Fund of America Class R-6		20,175,898
Prudential Jennison	Prudential Jennison Large Cap Growth Fund		93,129,326
Fidelity	Fidelity Mid Cap Index		42,611,039
Dimensional Fund Advisors	DFA Real Estate Securities Portfolio Institutional Class		12,999,376
Northern Trust	Active Multi-Manager Emerging Markets Equity Fund		10,904,155
PIMCO	PIMCO Rae US Small Fund Institutional Class		23,518,042
Harbor	Harbor International Fund		51,132,452
American Century	American Century Small Cap GR R6		21,645,481
Blackrock	Blackrock Global Allocation Fund		3,951,024
Total mutual funds			280,066,793
Common stock:
*Kirby Corporation	Common stock		53,677,515
*Participant loans	Interest rates ranging from 4.0% to 10.3% and maturity dates from January 7, 2026 to March 15, 2039		28,882,175
Total assets (held at end of year)		$	944,707,449

* Parties in interest to the Plan

See accompanying report of independent registered public accounting firm.

Fair Value Measurements - Schedeule of Investments Measured at Fair Value on a Recurring Basis (Details) - EBP 004 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	$ 915,825,274	$ 822,557,690
Mutual Funds
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	280,066,793	250,926,227
Company Common Stock
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	53,677,515	53,035,000
Total Assets in the Fair Value Hierarchy
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	333,744,308	303,961,227
Common Trust Funds
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	582,080,966	518,596,463
Level 1 \| Mutual Funds
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	280,066,793	250,926,227
Level 1 \| Company Common Stock
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	53,677,515	53,035,000
Level 1 \| Total Assets in the Fair Value Hierarchy
EBP, Investment, Fair Value and NAV [Line Items]
Investments, at fair value	$ 333,744,308	$ 303,961,227

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Description of Plan - Additional Information (Details) - EBP 004 - USD ($)

12 Months Ended

Dec. 31, 2025

Dec. 31, 2024

Jul. 01, 2025

Jul. 01, 2024

Participants age 50 or older, catch-up contribution

$ 7,500

Participants age 60 through 63, catch-up contribution

$ 11,250

Matching employer contribution

100.00%

Percentage on employee's eligible compensation

3.00%

Additional employer discretionary contribution percentage

5.00%

Additional employer discretionary contribution

$ 17,629,538

17,100,956

Profit Sharing contribution

$ 4,496,498

$ 4,260,826

Forfeitures from non-vested accounts to reduce the Plan's matching contributions

$ 2,173,357

1,992,488

EBP, Automatic deferral rate

3.00%

Receivable from participants, account, maximum borrowing, to total account, percentage

50.00%

Receivable from participants, maximum borrowing amount

$ 50,000

Participant loan fixed rate

1.00%

Participant loan maturity date

^[1]

Mar. 15, 2039

Involuntary termination, direct payment to participant

$ 1,000

Employee benefit plans vested percentage

100.00%

Total forfeitures

$ 365,520

$ 192,586

Maximum

Employee contribution percentage

50.00%

Participant loan interest rate

^[1]

10.30%

Participant loan maturity date

Mar. 15, 2039

Involuntary terminations, automatic distribution of participant accounts

$ 5,000

Minimum

Participant loan interest rate

^[1]

4.00%

Participant loan maturity date

Jan. 07, 2026

Involuntary terminations, automatic distribution of participant accounts

$ 1,000

Non-Highly Compensated Employees

Employee contribution percentage

50.00%

Highly Compensated Employees

Employee contribution percentage

17.00%

[1]	Parties in interest to the Plan

Fair Value Measurements

12 Months Ended

Dec. 31, 2025

EBP, Investment, Fair Value and NAV [Line Items]

Fair Value Measurements

(8)

Fair Value Measurements

The accounting guidance for using fair value to measure certain assets and liabilities establishes a three-tier value hierarchy, which prioritizes the inputs to valuation techniques used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little, if any, market data exists, therefore requiring an entity to develop its own assumptions about the assumptions that market participants would use in pricing the asset or liability.

The following is a description of the valuation methodologies used for Plan’s financial instruments and the classification of such instruments within the valuation hierarchy.

Mutual Funds

These instruments are public investment vehicles valued using the net asset value provided by the administrator of the fund. The net asset value price is quoted on an active market and is classified within Level 1 of the valuation hierarchy.

Company Common Stock

Company common stock is valued at the closing price listed by the New York Stock Exchange and is classified within Level 1 of the valuation hierarchy.

Common Trust Funds

These instruments are investment vehicles valued using the net asset value provided by the administrator of the fund. The net asset value is used as a practical expedient to determine fair value. Each collective trust provides for redemptions by the Plan at reported net asset values per share, with little to no advance notice requirement.

The methods described above may produce a fair value calculation that may not be indicative of net asset value or reflective of future fair values. Furthermore, while the Plan’s valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date.

The following tables summarize the Plan’s investment assets measured at fair value on a recurring basis at December 31, 2025 and 2024:


	December 31, 2025
	Level 1		Total Fair Value
Mutual funds	$	280,066,793	$	280,066,793
Company common stock		53,677,515		53,677,515
Total assets in the fair value hierarchy	$	333,744,308		333,744,308
Common trust funds				582,080,966
Investments at fair value			$	915,825,274


	December 31, 2024
	Level 1		Total Fair Value
Mutual funds	$	250,926,227	$	250,926,227
Company common stock		53,035,000		53,035,000
Total assets in the fair value hierarchy	$	303,961,227		303,961,227
Common trust funds				518,596,463
Investments at fair value			$	822,557,690

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

The entire disclosure for fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).

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Summary of Significant Accounting Policies (Policies) - EBP 004	12 Months Ended
	Dec. 31, 2025
EBP, Accounting Policy [Line Items]
Basis of Presentation	(a) Basis of Presentation The accompanying financial statements have been prepared on the modified cash basis, which is a comprehensive basis of accounting other than U.S. generally accepted accounting principles (“GAAP”), and is an acceptable method of reporting under Department of Labor regulations. The modified cash basis of accounting utilizes the cash basis of accounting while carrying investments at fair value and recording investment income (loss) on the accrual basis. Consequently, contributions are recognized when received rather than when earned, and expenses are recognized when paid rather than when the obligation is incurred. As of December 31, 2025, all employee contributions had been remitted to the trust and $174,613 of employer contributions were not remitted to the trust for the 2025 Plan year. As of December 31, 2024, all employee contributions had been remitted to the trust and $154,086 of employer contributions were not remitted to the trust for the 2024 Plan year. There were no material excess deferrals as of December 31, 2025 or 2024. Under GAAP, these amounts would have been reflected as accounts receivable and accounts payable, respectively. Certain other receivables are recorded in the statements of net assets available for benefits to reflect the accrued income, pending settlements and other transactions.
Use of Estimates	(b) Use of Estimates The preparation of financial statements requires Plan management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and disclosure of contingent assets and liabilities, and changes therein. Actual results could differ from those estimates.
Investment Valuation and Income Recognition	(c) Investment Valuation and Income Recognition Investments are reported at fair value. Purchases and sales of investments are recorded on a trade date basis. Net appreciation (depreciation) in fair value of investments includes realized gains and losses on investments sold during the year as well as net appreciation (depreciation) of the investments held at the end of the year. Interest and dividend income is accrued in the period earned. The Plan invests in investment contracts through The Invesco Stable Value Retirement Fund which is a common trust fund that primarily invests in guaranteed investment contracts (“GICs”) and synthetic GICs and is presented at fair value as of December 31, 2025 and 2024.
Contributions	(d) Contributions Contributions from Plan participants and the matching contributions from the Company are recorded in the year in which they are deposited in the trust.
Notes Receivable from Participants	(e) Notes Receivable from Participants Notes receivable from participants represent loans that are recorded at their unpaid principal balance plus any accrued but unpaid interest.
Benefit Payments	(f) Benefit Payments Payments to participants are recorded as the benefits are paid.