The Union Theatre is a small fringe theatre situated in the borough of Southwark in London, England. It was established in 1998 by Sasha Regan who took the initiative to convert a disused paper warehouse on Union Street near Southwark station into a functioning theatre. Set beneath railway arches, it is one of the more distinctive theatrical spaces in London.
The Union has a reputation for staging high-quality musicals in its tiny studio space. Some of its acclaimed productions include Stephen Sondheim's Sweeney Todd, Adler and Ross' The Pajama Game, Gilbert and Sullivan's The Mikado (an all-male version) and HMS Pinafore. The Union won the accolade of Best Up-and-Coming Theatre in the 2008 Empty Space Peter Brook Awards. The Union hosted the London premier of a new musical, Once Upon A Time At The Adelphi, in March 2010.
In July 2016, after almost twenty years in its original premises, the Union Theatre moved into new, specially-built premises just across the road from its original site. The theatre's new home, which "will keep the heart of the Union intact," offers a restaurant, rehearsal room, and some offices to let. Enhanced facilities include tiered seats and an increased seating capacity.