Known as Gyez in 1227, then Giez in 1289, Gy has been inhabited since Roman times.
Initially part of the Saint-Victor priory’s lands, it became part of Geneva's jurisdiction in 1754. In 1798, Jussy became a Geneva commune, including Gy, which became an independent commune in 1850.
The first Reformed temple in the Geneva countryside was built in Gy (1609-1611).