Montfort-l'Amaury (French pronunciation: [mɔ̃fɔʁ lamoʁi]) is a commune in the Yvelines department in the Île-de-France region, Northern France.

It is located at the foot of low hills, at about 130 m above sea level.

King Robert II built a castle in 996 in the hills of Montfort.

Montfort-l'Amaury was the stronghold of the Montfort family from the start of the 11th century.

The castle was destroyed by the English during the Hundred Years' War.