Frontignan is located in the Languedoc coastal plain between the towns of Sète and Montpellier.

The town is surrounded by the Gardiole mountain range in the north, the Ingril lagoon in the east, the Étang de Thau in the west and the Mediterranean shore (including the beach resort Frontignan-Plage) in the south.

The Rhône-Sète canal separates the inland town centre and Frontignan-Plage.