Saint-Yvi (; before September 2005: Saint-Yvy, ) is a commune in the Finistère department of Brittany in north-western France.
Inhabitants of Saint-Yvi are called in French Saint-Yviens. The population has been increasing quickly since the year 1975.
Saint-Yvi is located east of Quimper. Historically, the town belongs to Cornouaille. The river Jet forms its northern border.