St. Mark's Hospital (informally St. Mark's) is a hospital located near Harrow in northwest London, England. It is in the northwest corner of the London Borough of Brent, adjacent with the boundary of the London Borough of Harrow. It is the only hospital in the world to specialise entirely in intestinal and colorectal medicine and is a national and international referral centre for intestinal and colorectal disorders.[It is the only hospital in the UK, and one of only 14 worldwide, to be recognised as a centre of excellence by the World Organisation of Digestive Endoscopy.