Mordecai Oliver (22 October 1819-25 April 1898) was a member of the US House of Representatives (W-MO 4) from 4 March 1853 to 3 March 1857, succeeding Willard Preble Hall and preceding James Craig. Born in Anderson County, Kentucky, he practiced law in Richmond, Missouri before serving in Congress, as Secretary of State of Missouri in 1861, and as a judge in St. Louis.