Missouri gubernatorial special election, 1857

The Missouri gubernatorial special election of 1857 was Missouri's twelfth gubernatorial election. 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. 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.