| Election Name: | 1866 Massachusetts gubernatorial election |
| Country: | Massachusetts |
| Type: | presidential |
| Ongoing: | No |
| Previous Election: | 1865 Massachusetts gubernatorial election |
| Previous Year: | 1865 |
| Next Election: | 1867 Massachusetts gubernatorial election |
| Next Year: | 1867 |
| Image1: | File:AlexanderBullock.jpg |
| Nominee1: | Alexander Bullock |
| Party1: | Republican Party (United States) |
| Popular Vote1: | 91,980 |
| Percentage1: | 77.46% |
| Nominee2: | Theodore Sweetser |
| Party2: | Democratic Party (United States) |
| Popular Vote2: | 26,671 |
| Percentage2: | 22.46% |
| Governor | |
| Before Election: | Alexander Bullock |
| Before Party: | Republican Party (United States) |
| After Election: | Alexander Bullock |
| After Party: | Republican Party (United States) |
The 1866 Massachusetts gubernatorial election was held on November 6.
Governor Alexander Bullock was re-elected to a second term in office, defeating Democrat Theodore Sweetser.