Santo Stefano di Magra is a comune located in the Province of La Spezia within the Liguria region of Italy. Geographically, it is situated approximately 80 kilometres southeast of Genoa and about 11 kilometres northeast of La Spezia.
The municipality is positioned near the confluence of the Vara torrent into the Magra river. It is notably part of the Montemarcello-Magra Natural Regional Park and serves as a location for an entrance and exit to the toll-paying "Autostrada" highway system.