Simon I de Montfort (c. 1025 – 25 September 1087) was a French nobleman. He was born in Montfort l'Amaury, Duchy of Normandy (now in Ile de France), Kingdom of France. At his death he was buried about 20 miles (32 km) away in Epernon, Duchy of Normandy (now in Eure-et-Loir department), because it was the site of the fortress he was instrumental in constructing. He was the son of Amaury I de Montfort (c. 1000–1031) and Bertrade de Gometz.
Simon I first married Isabel de Broyles (b. 1034, Broyes, Marne, France), daughter of Hugh Bardoul. Their children were: