Terrassa (Catalan pronunciation: [təˈrasə], Spanish: Tarrasa) is a city in the east central region of Catalonia, Spain, in the comarca of Vallès Occidental, of which it is the co-capital along with Sabadell, the historic capital.

The city is located in the Catalan Prelitoral depression (Depressió Prelitoral), at the feet of the Prelitoral mountain range (Natural reserve of Sant Llorenç del Munt) and the average altitude of the city is 277 meters above sea level. It is 28 and 20 kilometres from Barcelona and Montserrat respectively.