Jaffna Fort is a fort built by the Portuguese at Jaffna, Sri Lanka, in 1618 under Phillippe de Oliveira following the Portuguese invasion of Jaffna. The fort is located near the coastal village of Gurunagar.

In 1795, it was taken over by the British, and remained under the control of a British garrison until 1948. As the only large military fort in the country, because of the presence of only government and military buildings within its ramparts, it was garrisoned by a detachment of the Ceylon Army.

Buildings inside the fort include the governor’s residence (King’s House), Queen’s House, Kruys Church, the Garrison Parade Ground, Police quarters and several buildings from the Portuguese era.