Longuyon (French pronunciation: [lɔ̃ɡɥijɔ̃]) is a commune in the Meurthe-et-Moselle department in the Grand Est region of north-eastern France.

Longuyon is located at the confluence of the Chiers and Crusnes rivers 18 kilometres (11 mi) and southwest of the commune of Longwy.

The town is named after a "long ford" (from the Latin longa guada) that allowed crossing of the Chiers in Roman times.

The apartment blocks on the southwestern edge of town, still called "La Cité Canadienne", were home to Royal Canadian Air Force staff and their families in the 1950s and 1960s, when the RCAF had an airbase at nearby Marville.

The St. Agatha monastery was converted to a collegiate church in 973 by the Archbishop of Trier, then into a Benedictine priory in the late twelfth century.

The current building was built in the late twelfth and early thirteenth centuries; the base of the tower appears to be slightly earlier.