Saint-Lizier (French pronunciation: [sɛ̃ lizje]; Occitan: Sent Líser) is a commune in the Ariège department in southwestern France, situated on the river Salat.

Saint-Lizier has a rich history stretching back to pre Gallo-Roman times.

In 72 BC, Pompey, returning from his triumphs in Spain against Sertorius, stopped here.

The ramparts seen today date from 3rd century AD and enclose the oppidum.

During the fifth century, the citadel became an episcopal see, the oldest in the Ariège area.