43 (2021 population: 352) is a rural municipality (RM) in the Canadian province of Saskatchewan within Census Division No.

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

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

[3] The reeve position is vacant while the RM's administrator is Vickie Greffard.

[3] The RM is a part owner of the Fife Lake Railway.