Saint-Marcellin-en-Forez (French pronunciation: [sɛ̃ maʁsəlɛ̃ ɑ̃ fɔʁɛ], literally Saint-Marcellin in Forez; Occitan: Sant Marcelin) is a commune in the Loire department in central France.

[3] Saint-Marcellin-en-Forez is at an ancient crossroads between Burgundy and Velay, on the highway from the Forez and Montbrison toward the only bridge known in the south of the Loire, which was at Saint-Rambert.

The origins of the city date back to the early Middle Ages.

The earliest written reference to the town dates from 984, but a treasure of about 500 4th-century coins (discovered in 1884) indicates an even earlier settlement.

The old town, topped by a high tower, was a defensive structure that withstood repeated assaults.