Alonsa is a rural municipality (RM) in the province of Manitoba in Western Canada. It lies on the west side of Lake Manitoba. The Ebb and Flow 52 Indian reserve is located within the borders of the municipality. The 6 ha Margaret Bruce Beach Provincial Park is located within the RM, 12 kilometres east of the town of Alonsa, on one of a series of sand ridges that extend the length of the west side lake. The park is currently under lease to a private operator but development plans include a provincial campground and day use facility.
The incorporation of Alonsa on 1 January 1945 was as a Local Government District (LGD). It received RM status on 1 January 1997.
Coordinates: 50°58′41″N 99°03′12″W / 50.97806°N 99.05333°W