The Rural Municipality of Moosomin No. 121 (2016 population: ) is a rural municipality (RM) in the Canadian province of Saskatchewan within Census Division No. 5 and Division No. 1. It is located in the southeast portion of the province.
The RM of Moosomin No. 121 incorporated as a rural municipality on January 1, 1913.
Moosomin and District Regional Park, upstream from Moosomin Dam, and Moosomin Lake are located in the RM. The black swallowtail (papilio polyxenes asterius), a species of special concern, makes its home in this area.
The following urban municipalities are surrounded by the RM.
The following unincorporated communities are within the RM.
In the 2021 Census of Population conducted by Statistics Canada, the RM of Moosomin No. 121 had a population of living in of its total private dwellings, a change of from its 2016 population of . With a land area of , it had a population density of in 2021.
In the 2016 Census of Population, the RM of Moosomin No. 121 recorded a population of living in of its total private dwellings, a change from its 2011 population of . With a land area of , it had a population density of in 2016.
Moosomin is home to the Red Lily Wind Farm and Moosomin Lake Regional Park.
The RM of Moosomin No. 121 is governed by an elected municipal council and an appointed administrator that meets on the second Thursday of every month. The reeve of the RM is David Moffatt while its administrator is Kendra Lawrence. The RM's office is located in Moosomin.
Highway 1 (the Trans-Canada Highway) and Highway 8 intersect within this RM.