Major-General William Nairn Forbes (3 April 1796 – 1 May 1855) was a British architect and military engineer in the Bengal Army. He was responsible for the design of the Anglican St Paul's Church, Calcutta (1839–47) in Bengal during Company rule in India, now the cathedral of the Diocese of Calcutta and sited in Kolkata, India. Forbes was also architect in 1831 of the Greek Revival Calcutta Silver Mint and drew inspiration for the portico from the Parthenon in Athens.