Saint-Cergue is a municipality in the district of Nyon in the canton of Vaud in Switzerland.
Saint-Cergue is first mentioned in 1110 as ecclesiam Sancti Cyrici.
Saint-Cergue has an area, as of 2009, of 24.3 square kilometers (9.4 sq mi). Of this area, 6.71 km2 (2.59 sq mi) or 27.6% is used for agricultural purposes, while 16.02 km2 (6.19 sq mi) or 66.0% is forested. Of the rest of the land, 1.41 km2 (0.54 sq mi) or 5.8% is settled (buildings or roads) and 0.13 km2 (32 acres) or 0.5% is unproductive land.
Of the built up area, housing and buildings made up 3.3% and transportation infrastructure made up 2.2%. Out of the forested land, 62.6% of the total land area is heavily forested and 3.4% is covered with orchards or small clusters of trees. Of the agricultural land, 0.0% is used for growing crops and 2.1% is pastures and 25.5% is used for alpine pastures.
The municipality was part of the Nyon District until it was dissolved on 31 August 2006, and Saint-Cergue became part of the new district of Nyon.