Brentwood:1 Uninc. town (1990 pop. 45,218), Suffolk co., SE N.Y., on central Long Island, in the town of Islip. It is mainly residential, with various light industries. Josiah Warren led (1851) an experiment in communal living in Brentwood. A campus of the New York Institute of Technology is there.2 Borough (1990 pop. 10,823), Allegheny co., W Pa., a residential suburb of Pittsburgh; inc. 1915.

Brentwood, city (1991 pop. 51,212) and district, Essex, SE England. Brentwood is mainly residential but produces some agricultural equipment, film, and prefabricated concrete. The city was located on an important coach road from London to Colchester. The 15th-century White Hart Inn still stands. Brentwood School was founded in the 16th cent.