Seaford House, originally called Sefton House, at 37 Belgrave Square is an aristocratic mansion in London, England. It is the largest of the three detached houses which occupy three corners of Belgrave Square in the district of Belgravia. Seaford House is a white stucco building with four main stories. Dated 1842, it was designed by Philip Hardwick for the Earl of Sefton. Seaford House and its railings and gate piers have been listed Grade II* for their architectural merit.