Fort William is a fort built in Calcutta on the eastern banks of the River Hooghly, the major distributary of the River Ganges, during the early years of the Bengal Presidency of British India. It was named after King William III of England and Ireland and II of Scotland. In front of the Fort is the Maidan, which used to be a part of the Fort and is the largest urban park in Calcutta.
There are actually two Fort Williams, the old and the new. The original was built in 1696 by the British East India Company under the supervision of John Goldsborough. Sir Charles Eyre started construction near the bank of the River Hooghly with the South-East Bastion and the adjacent walls. It was named after King William III in 1700.
John Beard, his successor, added the North-East Bastion in 1701, and in 1702 started the construction of the Government House (Factory) at the centre of the fort. Construction ended in 1706. The original building had two stories and projecting wings. An internal guard room became the Black Hole of Calcutta.
In 1756, the Nawab of Bengal, Siraj Ud Daulah, attacked the Fort, temporarily conquered the city, and changed its name to Alinagar. This led the British to build a new fort in the Maidan.
The Fort is built of brick and mortar in the shape of an irregular octagon with an area 5 km². Five of its sides face landward, and three towards the Hooghly River. The design is that of a star fort, suited to defence against cannon, but from before the advent of explosive shells.
It is surrounded by a dry moat 9 m deep and 15 m broad, which can be flooded but is designed as an area in which to use enfilade (or "flanking") fire against any attackers reaching the walls. There are six gates: Chowringhee, Plassey Calcutta, Water Gate St Georges and the Treasury Gate. There are similar forts at places like Thalassery in Kerala. It has 9-hole golf course currently.