University College School, also known as UCS, is a private day school in Frognal, Hampstead, London, England. The school was founded in 1830 by University College London.

The UCS Hampstead Foundation is composed of three main entities: the Pre-Prep (previously known as The Phoenix School) for ages 3 to 7 on the Finchley Road site, acquired by UCS in 2003; the Junior Branch, for boys aged 7 to 11 on the Holly Hill site in Hampstead; and the Senior School, for boys aged 11 to 16 and co-educational for ages 16 to 18 on the Frognal site, which is the largest school site. The main campus and the Great Hall are noted examples of Edwardian architecture. Inside the hall is a Walker pipe organ, used for school concerts, professional recordings and other festivities. The school also owns playing fields situated in Ranulf Road in West Hampstead, used for training, physical education and sporting fixtures.

UCS is a member of the Eton Group of twelve independent schools and the Headmasters' and Headmistresses' Conference. It has ties with the Equatorial College School in Uganda.