The Unicorn Theatre is a children's theatre in the London Borough of Southwark, in England. It is a custom-built, RIBA Award–winning building on Tooley Street, which opened in 2005. The theatre was designed by Keith Williams, built by Arup and comprises two theatre spaces (the Weston and Clore Theatres), an education studio, rehearsal space, café and the John Lyon meeting room.

The theatre was founded in 1949, by Caryl Jenner, originally as a mobile theatre; In 1961, Jenner began presenting children's productions at the Arts Theatre in the West End, and in 1967 the company took over the lease of the theatre which then became Unicorn's permanent performing base until 1999; during this period the normal run of adult performances continued during the evenings.

The Unicorn is a registered charity and is an Arts Council England National Portfolio organisation.