Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 27, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity File Number	001-40893
Entity Registrant Name	CATALYST BANCORP, INC.
Entity Incorporation, State or Country Code	LA
Entity Tax Identification Number	86-2411762
Entity Address, Address Line One	235 N. Court Street
Entity Address, City or Town	Opelousas
Entity Address State Or Province	LA
Entity Address, Postal Zip Code	70570
City Area Code	337
Local Phone Number	948-3033
Title of 12(b) Security	Common Stock (par value $.01 per share)
Trading Symbol	CLST
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 63.5
Entity Common Stock, Shares Outstanding		5,058,612
Entity Central Index Key	0001849867
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	Castaing, Hussey & Lolan, LLC
Auditor Firm ID	447
Auditor Location	New Iberia, LA