Casimir Grelewski
- categories: male , martyr , presbyter
- date of birth: 20.02.1907
- date of death: 09.01.1942
- beatification: 13.06.1999 (ceremonially)
- canonization: non-existence
- other Roman Martyrology days: 09.01.
- other memorial days: non-existence
- order: non-existence
- order founder: non-existence
- forenames: Casimir
- surnames: Grelewski
- epithets: non-existence