Saint-Martin-de-Crau (; Provençal: Sant Martin de Crau) is a commune in the Bouches-du-Rhône department in southern France. Inhabitants are called Saint-Martinois.
Saint-Martin-de-Crau has the lowest population density of all communes in metropolitan France that have a population exceeding 12,000 inhabitants. With a land area of 214.87 km<sup>2</sup> (82.962 sq mi), it is the fifth-largest commune in geographic area in metropolitan France (after Arles, Saintes-Maries-de-la-Mer, Laruns, and Marseille).
Saint-Martin-de-Crau is twinned with: