Duncannon Fort, Star fort with lighthouse on Hook Peninsula, County Wexford, Ireland.

Duncannon Fort is a star-shaped fortification on Hook Peninsula, built with bastions, ramparts, and underground passages. A lighthouse crowns the structure and overlooks part of Waterford Harbour.

The fort was built in 1587 by Queen Elizabeth I to defend against Spanish Armada threats. It later witnessed multiple sieges during the Irish Confederate Wars.

The fort became notorious as the execution site of the Croppy Boy, a rebel figure commemorated in the ballad 'The Croppy Boy'. In 1798 the fort stayed loyal to the Crown and served as a prison and execution ground for United Irishmen rebels.

The fort stands on a peninsula on the east side of Waterford Harbour, with the 1774 lighthouse still in use at the site. The landward side is protected by a deep ditch, a medieval wall and caponiers, and the east wall was raised in 1606 against fire from Windmill Hill. Parts of the site are exposed to harbour weather, so allow for wind and rain.

In 1690 the fort hosted two kings within months: James II sailed from the spot still called King James' Hole on 3 July, and William III stayed in September when bad weather delayed his return to England.