Simon I de Montfort (c. 1025 – 25 September 1087) was a French nobleman. He was born in Montfort l'Amaury, in the Duchy of Normandy, and became its lord. He was the son of Amaury I of Montfort (c. 1000–1031) and Bertrade. At his death he was buried about 20 miles (32 km) away in Epernon, because it was the site of the fortress he was instrumental in constructing.
Simon I first married Isabel de Broyes (b. 1034, Broyes, Marne, France), daughter of Hugh Bardoul. Their children were:
Amauri II de Montfort (c. 1056–1089), lord of Montfort