Fontenay-lès-Briis (French pronunciation: [fɔ̃tnɛ lɛ bʁi] ⓘ, literally Fontenay near Briis) is a commune in the Essonne department in Île-de-France in northern France.

The village of Fontenay-lès-Briis is mentioned in the charter of Clotilde, dated to 10 March 673, founding a nunnery at Bruyères-le-Châtel.

The average annual rainfall is 696.0 mm (27.40 in) with December as the wettest month.

The temperatures are highest on average in July, at around 19.8 °C (67.6 °F), and lowest in January, at around 4.4 °C (39.9 °F).

Inhabitants of Fontenay-lès-Briis are known as Fontenois in French.