| 2021 Offaly Senior B Hurling Championship | |
| Dates: | 28 August - 20 November 2021 |
| Teams: | 6 |
| Sponsor: | Molloy Environmental |
| Champions: | Clodiagh Gaels |
| Count: | 1 |
| Champions Captain: | Shane Dolan |
| Champions Manager: | Paul Murphy |
| Runners-Up: | Tullamore |
| Runners-Up Manager: | Kevin Martin |
| Relegated: | Shinrone |
| Matches: | 19 |
| Previous Year: | 2020 |
| Previous Tournament: | 2020 Offaly Senior B Hurling Championship |
| Next Year: | 2022 |
| Next Tournament: | 2022 Offaly Senior B Hurling Championship |
The 2021 Offaly Senior B Hurling Championship was the fourth staging of the Offaly Senior B Hurling Championship since its establishment by the Offaly County Board. The group stage fixtures were confirmed on 27 May 2021.[1] The championship ran from 28 August to 20 November 2021.
The final was played on 20 November 2021 at St Brendan's Park in Birr, between Clodiagh Gaels and Tullamore, in what was their first ever meeting in the final. Clodiagh Gaels won the match by 2–10 to 1–12 to claim their first ever championship title.[2]
Promoted from the Offaly Intermediate Hurling Championship
Promoted to the Offaly Senior Hurling Championship[4]
Relegated to the Offaly Intermediate Hurling Championship