University College, informally known as Castle, is the oldest constituent college of the University of Durham in England. Centred on Durham Castle on Palace Green, it was founded in 1832 by William van Mildert, Bishop of Durham. As a constituent college of Durham University, it is listed as a higher education institution under section 216 of the Education Reform Act 1988. Almost all academic activities, such as research and tutoring, occur at a university level.

The Colleges of Durham University are residential colleges that are the primary source of accommodation and support services for undergraduates and postgraduates at Durham University, as well as providing a focus for social, cultural and sporting life for their members, and offering bursaries and scholarships to students. They also provide funding and/or accommodation for some of the research posts in the University. All students at the University are required to be members of one of the colleges.