Dauphin Lake was named for the heir to the French throne in 1739 by Francois de La Verendrye. It is in western Manitoba near the city of Dauphin, Manitoba. The lake covers an area of 200 square miles (520 km2) and has a drainage basin of about 3,250 square miles (8,400 km2). The Mossey River drains the lake into Lake Winnipegosis. The basin is drained by seven major streams and has a total relief of 1,900 feet (580 m). The lake is located within the territory of three rural municipalities; in descending order of area they are the Rural Municipality of Ochre River, the Rural Municipality of Dauphin, and the Rural Municipality of Mossey River.
Several efforts have been made to control lake levels in the last century. In 1964 the Mossey River Dam was constructed at Terin's Landing at the outlet of the lake. The ten bay concrete stoplog structure complete with a fish ladder is operated by the Province. The summer target since 1993 has been 854.8 feet (260.54 m). The dam can restrict the outflow when conditions are dry and levels low but the river limits the outflow when the lake is high.
Regulation of the lake is difficult. Conditions can change very quickly. For example a four day rain in June 1947 produced an estimated peak inflow of 60,000 cubic feet per second (1,700 m3/s). At normal levels, the Mossey river can only take out about 500 cubic feet per second (14 m3/s).
The lake provides wonderful recreational opportunities. Fishing is popular in both winter and summer, many people camp on the lake's shores and there are many cottages.