| Trumpler 3 | |
| Epoch: | J2000.0 |
| Constellation: | Cassiopeia |
| Dist Ly: | 2250 ly |
| Dist Pc: | 690 pc |
| Appmag V: | 7.0[1] |
| Names: | Cr 36, Cl Harvard 1, C 0307+630 |
Trumpler 3 is an open cluster located in the constellation Cassiopeia. It has the visual magnitude of 7 and is one of the most famous star clusters in the Trumpler catalogue.
It has two bright stars, TYC 4053-658-1 and TYC 4053-466-1 of apparent magnitudes 10.16 and 10.02, respectively.