| Election Name: | 1851 Boston mayoral election |
| Type: | Presidential |
| Ongoing: | no |
| Previous Election: | 1850 Boston mayoral election |
| Previous Year: | 1850 |
| Election Date: | Dec. 8, 1851 (1st vote) Dec. 17, 1851 (2nd vote) Dec. 24, 1851 (3rd vote) |
| Next Election: | 1852 Boston mayoral election |
| Next Year: | 1852 |
| Mayor | |
| Before Election: | John P. Bigelow |
| Before Party: | Whig Party (United States) |
| After Election: | Benjamin Seaver |
| After Party: | Whig Party (United States) |
| 1Blank: | First vote |
| 2Blank: | Second vote |
| 3Blank: | Third vote |
| Image1: | File:Benjamin Seaver 5210004 015 013 (3x4).jpg |
| Candidate1: | Benjamin Seaver |
| Party1: | Whig Party (United States) |
| 1Data1: | Did not contest |
| 2Data1: | 3,970 47.31% |
| 3Data1: | 3,990 50.05% |
| Candidate2: | John H. Wilkins |
| Party2: | Whig Party (United States) |
| 1Data2: | 4,423 45.13% |
| 2Data2: | Did not contest |
| 3Data2: | Did not contest |
| Image4: | Jerome V. C. Smith by E. Billings 5210004 015 014 (3x4a).jpg |
| Candidate4: | Jerome V. C. Smith |
| Party4: | Know Nothing |
| 1Data4: | 2,672 27.26% |
| 2Data4: | 2,680 31.94% |
| 3Data4: | 2,736 34.32% |
| Image5: | Adam W. Thaxter, Jr. 12700882257 4 (1).jpg |
| Candidate5: | Adam W. Thaxter Jr. |
| Party5: | Democratic Party (United States) |
| 1Data5: | 1,250 21.95% |
| 2Data5: | 1,290 15.37% |
| 3Data5: | 1,024 12.84% |
The 1851 Boston mayoral election saw the election of Benjamin Seaver, a former president of the Boston Common Council, as mayor of Boston. The election took three votes, as no candidate secured the needed majority in the first two attempts. In the third attempt, Seaver won the required majority by the margin of a single vote. Incumbent Whig mayor John P. Bigelow was not a nominee for reelection.
| Vote round | Other candidate | Scattering | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Nominee | % | Nominee | % | Nominee | % | Nominee | % | Candidate | % | % | |
| 1st | John H. Wilkins | 45.13 | Adam W. Thaxter Jr | 21.95 | 27.26 | George F. Williams | 4.85 | colspan=2 | 0.83 | ||
| 2nd | 47.31 | 15.37 | 31.94 | 2.91 | Henry B. Rogers | 1.88 | 0.60 | ||||
| 3rd | 50.05 | 12.84 | 34.32 | colspan=2 | 2.36 | 0.48 | |||||