It is a coastal municipality covering an area of 195,47 km² and is limited to the north by the municipalities of Almada and Seixal, to the northeast by Barreiro, to the east by Setúbal and to the south and west by the Atlantic Ocean.

The estuary of the Sado river, the Serra da Arrábida, Cape Espichel, the lagoon of Albufeira and Meco beach are part of the natural landscape of Sesimbra.