251 (2016 population: 191) is a rural municipality (RM) in the Canadian province of Saskatchewan within Census Division No.

It is located in the southern portion of the province near Last Mountain Lake northwest of Regina.

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

251 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 Sheldon Vance while its administrator is Yvonne (Bonny) Goodsman.