The Rural Municipality of Gull Lake No. 139 (2016 population: ) is a rural municipality (RM) in the Canadian province of Saskatchewan within Census Division No. 8 and Division No. 3. It is located in the southwest portion of the province.
The RM of Gull Lake No. 139 incorporated as a rural municipality on January 1, 1913.
In the 2021 Census of Population conducted by Statistics Canada, the RM of Gull Lake No. 139 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 Gull Lake No. 139 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.
The following urban municipalities are surrounded by the RM.
The RM of Gull Lake No. 139 is governed by an elected municipal council and an appointed administrator that meets on the second Tuesday of every month. The reeve of the RM is Elizabeth Kramer while its administrator is Jeanette Kerr. The RM's office is located in Gull Lake.