Fonthill Splendens was a country mansion in Wiltshire, built by Alderman William Beckford; building began in 1755 and was largely complete by 1770. The construction followed the destruction by fire of the previous Fonthill House. The new mansion had a life of only fifty years, being demolished in 1807.

Sir William Beckford was a Jamaican-born planter and Whig politician who twice served as Lord Mayor of London in 1762 and 1769. One of the best known political figures in Georgian era London, his vast wealth derived from the sugar plantations and hundreds of slaves he owned in the British colony of Jamaica. In Britain, Beckford was a supporter of the Whig party, including Prime Minister William Pitt, 1st Earl of Chatham. He also publicly supported progressive causes and frequently championed the London public.