| Petru Cazacu | |
| Office: | Prime Minister of the Moldavian Democratic Republic |
| Term Start: | 9 April 1918 |
| Term End: | 29 November 1918 |
| Predecessor: | Daniel Ciugureanu |
| Successor: | Union with Romania |
| President: | Ion Inculeț |
| Birth Date: | 6 October 1873 |
| Birth Place: | Chișinău |
| Death Date: | August 1956 |
| Death Place: | Bucharest |
| Profession: | Physician |
Petru Cazacu (; 6 October 1873 – August 1956) was a politician from Bessarabia (Moldova).
He served as the prime minister of the Moldavian Democratic Republic in 1918.