| Election Name: | 1857 Missouri gubernatorial special election |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1856 Missouri gubernatorial election |
| Previous Year: | 1856 |
| Next Election: | 1860 Missouri gubernatorial election |
| Next Year: | 1860 |
| Election Date: | August 7, 1857 |
| Nominee1: | Robert Marcellus Stewart |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 47,975 |
| Percentage1: | 50.18% |
| Nominee2: | James S. Rollins |
| Party2: | Know-Nothing |
| Popular Vote2: | 47,641 |
| Percentage2: | 49.82% |
| Governor | |
| Before Election: | Hancock Lee Jackson |
| Before Party: | Democratic Party (United States) |
| After Election: | Robert Marcellus Stewart |
| After Party: | Democratic Party (United States) |
The 1857 Missouri gubernatorial special election was held on August 7, 1857. The election was called to fill the remainder of the term of Trusten Polk, who had resigned in February 1857 upon his election to the United States Senate.[1] In the special election, held on August 7, 1857, the Democratic nominee, Robert Marcellus Stewart, defeated Know-Nothing candidate James S. Rollins (running under the American Party label) by a margin of only 334 votes. This was Rollins' second run for Governor of Missouri, having also lost in the 1848 gubernatorial election.