Terrassa, city, Barcelona provincia (province), in the comunidad autónoma (autonomous community) of Catalonia, in northeastern Spain. Terrassa lies along the coastal plain, just northwest of Barcelona city. The successor of Egara, a Roman town, it became in ad 450 an important episcopal see with a cathedral, later destroyed. Existing historic churches include the 12th-century Romanesque Santa María and San Pedro, both of which have a 6th-century apse; Santa María contains 9th-century primitive paintings. The baptistery of San Miguel probably dates from the 6th century. In the Santo Espíritu church, begun in 1575, is an alabaster figure of Christ sculpted in 1544. The 12th-century castle has undergone reconstruction and houses the Soler y Palet Museum, famous for its medieval paintings and sculpture and for its collection of Catalan ceramics. Also in Terrassa is the Biosca Museum of historic textiles and a school for textile engineers.
The city’s main economic activity has for centuries been the manufacture of woolens; other products are nylon, cottons, carpets, mosaics, and glass. There are also mechanical and electrical industries. Pop. (2007 est.) mun., 202,136.