| HD 128311 c | |
| Discoverer: | Vogt et al. |
| Discovery Site: |  California, United States |
| Discovered: | June 24, 2005 |
| Apsis: | astron |
| Aphelion: | 2.02AU |
| Perihelion: | 1.46AU |
| Semimajor: | 1.74± |
| Period: | 921.538± |
| Avg Speed: | 20.7 |
| Star: | HD 128311 |
HD 128311 c is an exoplanet located approximately 54 light-years away in the constellation of Boötes. This planet orbits in an eccentric orbit at 1.74 AU from its star (HD 128311). The planet has a minimum mass of 3.22, and astrometric observations in 2014 revealed its true mass to be 3.789 .