255 (2016 population: 475) is a rural municipality (RM) in the Canadian province of Saskatchewan within Census Division No.

[2] The RM's eastern boundary runs along the shore of Lake Diefenbaker.

In the 2021 Census of Population conducted by Statistics Canada, the RM of Coteau No.

255 is governed by an elected municipal council and an appointed administrator that meets on the second Monday of every month.

[3] The reeve of the RM is Terry Sieffert while its administrator is Lindsay Hargrave.