Saint-Cyr Lake /ˌseɪntˈsɪər/ is a freshwater body of water crossed by the Saint-Cyr River South in the north-eastern part of Senneterre, in La Vallée-de-l'Or Regional County Municipality (RCM), in the administrative region of Abitibi-Témiscamingue, in the province of Quebec, in Canada.

The hydrographic slope of Lake Saint-Cyr is accessible through a forest road (North-South direction) on the east side of the Saint-Cyr River Valley; in addition, another forest road (East-West direction) serves the northern part of the Saint-Cyr Lake Biodiversity Reserve and connects R1015 to the west.

The surface of Lac Saint-Cyr is usually frozen from early November to mid-May, however, safe ice circulation is generally from mid-November to mid-April.

This commission took into account that the course of the Saint-Cyr river belonged from now on to two hydrographic slopes as a result of the construction of an impoundment dam.

The toponym "lac Saint-Cyr" was made official on December 5, 1968 by the Commission de toponymie du Québec, when it was created.