The Rural Municipality of Winchester is a former rural municipality (RM) in the Canadian province of Manitoba. It was originally incorporated as a rural municipality on November 1, 1890. It ceased on January 1, 2015 as a result of its provincially mandated amalgamation with the Town of Deloraine to form the Municipality of Deloraine – Winchester.
The former RM is located in the southwestern part of the province, on its border with the state of North Dakota in the United States. It had a population of 594 in the 2006 census.
According to Statistics Canada, the former RM had an area of 725.58 km² (280.15 sq mi). A portion of Manitoba's Turtle Mountain Provincial Park is located at the southeast corner of the former RM along its border with North Dakota.
Coordinates: 49°10′39″N 100°25′56″W / 49.17750°N 100.43222°W