| Cover | Aug. 04, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 04, 2023 |
| Entity Registrant Name | The First Bancshares, Inc. |
| Entity Incorporation, State or Country Code | MS |
| Entity File Number | 000-22507 |
| Entity Tax Identification Number | 64-0862173 |
| Entity Address, Address Line One | 6480 U.S. Highway 98 West, |
| Entity Address, City or Town | Hattiesburg, |
| Entity Address, State or Province | MS |
| Entity Address, Postal Zip Code | 39402 |
| City Area Code | (601) |
| Local Phone Number | 268-8998 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | FBMS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000947559 |
| Amendment Flag | false |
