Église Saint-Maclou de Mantes, Romanesque church in Mantes-la-Jolie, France.

Église Saint-Maclou de Mantes is a former parish church in Mantes-la-Jolie, of which only the 16th-century tower and a section of Romanesque wall with two arches remain. The pale grey and beige stone tower rises in three tiers: a lower level with two large pointed arch openings and smaller arched niches, a middle stage with tall narrow arches, and an open lantern stage with vertical arches.

The building was constructed in the early 11th century but suffered destruction by fire in 1087 during William the Conqueror's military assault on the city. This devastating fire marked a turning point in both the church's history and the development of the city itself.

The church functioned as a place of worship and also as a hospital for the local community during medieval times. This combination of spiritual and practical care shows how closely religious life and everyday needs were intertwined in the medieval city.

The tower stands on the south side of the former church, above what was the second bay of the south aisle. The nave, choir and most walls were demolished by 1828, so only the 16th-century tower, a stretch of Romanesque wall with two arcades and the crypt remain. The tower was cleaned of its pollution film in the 1980s.

The church's floor plan deviates from the traditional East-West alignment, with its western facade angled slightly toward the northwest. This unexpected orientation breaks from standard church architecture conventions and invites questions about why this unusual choice was made.