William Watts (c. 1722 – 4 August 1764) was chief of the Kasimbazar (or Cossimbazar) factory of the British East India Company. He lived in Bengal, and he was proficient in Bengali, Hindustani and Persian languages.
Robert Clive assigned William Watts with the responsibility of acting as the representative of the company to the Nawab's court at Murshidabad.
Robert Clive engaged him to work out a secret plan for the final overthrow of Siraj Ud Daulah and to install a favourable Nawab on the masnad. Watts thus set up contact with the dissident amirs of the Murshidabad durbar including Mir Jafar, Rai Durlabh and Yar Lutuf Khan. William Watts played a role in forging the grand conspiracy against Siraj Ud Daulah which led to his final overthrow at the Battle of Plassey. On 5 June 1757 he personally visited Mir Jafar and obtained his oath of allegiance.
In recognition of his services he was given £114,000 from the Nawab's treasury and made the governor of Fort William on 22 June 1758, in place of Roger Drake who had deserted the fort when it was attacked and captured in June 1756. This had been the location of the Black Hole of Calcutta on 20 June 1756.
Four days later he resigned in favour of Robert Clive to return to England.
He wrote a book Memoirs of the Revolution in Bengal which was published in 1764.
On his return to England he built the South Hill Park mansion which lies to the south of Bracknell, Berkshire which is now an Arts Centre.