Firminy (French pronunciation: [fiʁmini]; Occitan: Frominiu) is a commune in the Loire department in central France.

It lies on the river Ondaine, 13 km southwest of Saint-Étienne by rail.

The ancient name of the town was Firminiaco or Firminiacus (lit.

Firminy had historically important coalmines known since the 14th century and extensive manufactures of iron, steel, and aluminum goods, including railway material, machinery and cannon.

The architect Le Corbusier designed a group of modern buildings, called "Firminy Vert", which includes the Saint-Pierre Church, a stadium, a cultural center, and an Unité d'Habitation.