Grestain Abbey (or Grestein Abbey, French: Abbaye Notre-Dame de Grestain) was an 11th-CenturyBenedictine monastery near the town of Fatouville-Grestain, which is located in the modern-day Eure départementof Upper Normandy, France. The abbey was in the Roman Catholic Diocese of Lisieux. Closely associated with the family of William, Duke of Normandy.