Missouri Territory was a historic, organized territory in the United States. It was originally known as the Louisiana Territory and was renamed on June 4, 1812 to avoid confusion with the state of Louisiana which joined the Union in 1812. Arkansas Territory was separated from Missouri Territory in 1819. The state of Missouri was separated out from the territory in August 10, 1821.

The remaining portion, consisting of the present states of Iowa, the Dakotas, and part of Minnesota effectively became unorganized territory after Missouri became a state. In 1834 the remaining territory was attached to Michigan Territory.

See also: Historic regions of the United States