Église Saint-Louis de Port-Marly, Catholic church in Le Port-Marly, France.

Église Saint-Louis de Port-Marly is a pale ashlar stone church with a grey hipped roof and a square bell tower topped by a lantern and cross. Its front facade carries a triangular pediment with a carved relief above a round-arched window, and a projecting porch with a rounded pediment on six columns stands to the right, reached by steps. Built 1778–1783 to plans by Étienne-François Legrand, it has a tower with louvered openings above the crossing.

Built from 1778 to 1783 to plans by architect Étienne-François Legrand, the church was founded with its first stone laid in the presence of King Louis XVI and his brothers, the future Louis XVIII and Charles X. It was classified as a monument historique in 1937. In 1985 the bishop of Versailles sought to introduce the new rite, and the parish resisted; the conflict peaked on 30 March 1987 when Father Bruno de Blignières was expelled by police while celebrating Mass, an episode known as the affaire du Port-Marly.

The parish kept the Latin Mass and Gregorian chant after 1985, when worshippers occupied the church against the bishop of Versailles' liturgical reforms. The priest Gaston Roussel, a composer of sacred music, had drawn a traditional-minded congregation from across the Yvelines and Paris. Since then the building has been served by the Institut du Christ Roi Souverain Prêtre and houses the chapel of Notre-Dame de France.

The church stands at 42 route de Versailles in Le Port-Marly. Its choir is oriented west rather than east, so the apse faces the street side opposite the usual arrangement; look for the six-column porch on the right of the facade. The building is a classified monument historique since 1937 and remains an active parish church, so visits fit around services.

What sets this church apart is that its choir faces west, departing from the typical design found in Catholic buildings. This architectural choice makes the structure worth noticing during a visit.