Église Sainte-Anne de Gassicourt, Romanesque church in Mantes-la-Jolie, France.

Église Sainte-Anne de Gassicourt is a Romanesque church in Mantes-la-Jolie built with a cross-shaped floor plan that includes a nave, transept, and flat choir. The building displays characteristic features of Norman Romanesque design throughout its structure and proportions.

Raoul IV, Count of Vexin, installed monks at Gassicourt shortly before his death in 1074; his son Simon, Count of Mantes, gave the monastery to the Cluny order, making it a Benedictine priory dedicated to Saint Sulpice. The monks rebuilt the church in Norman Romanesque style from the early 12th century, and it was placed under the patronage of Saint Anne. In 1295 Pope Boniface VIII's bull raised Gassicourt to a priory-deanery; Jacques-Bénigne Bossuet became commendatory prior-dean in 1660. The priory was sold in 1738 and the monks left the following year.

The choir stalls inside feature intricate oak carvings from the late 1400s that depict craftspeople and winemaking practices of that era. These details reveal what daily work and trades looked like for people living in the community at that time.

The church is located at 10 Impasse Sainte-Anne and remains an active parish church with regular services. It is advisable to check opening times in advance, as access may depend on scheduled services or visiting hours.

The round window above the west portal sits in a carved frame with two small figures attached at its sides and base. The portal below has a tympanum divided into small squares filled with stars, framed by archivolts decorated with rows of small circular openings. The square bell tower rises about 24 metres over the crossing, pierced on each side by three arched openings.