Mellifont was the first Cistercian monastery in Ireland, founded in 1142 by Saint Malachy with monks sent by Saint Bernard from Clairvaux. It was the leading abbey in the country until the Dissolution in 1539. Afterwards it became a fortified Tudor house, where the Treaty of Mellifont ended the Nine Years' War in 1603, and William of Orange used it as his headquarters before the Battle of the Boyne.
Little of the medieval abbey still stands to any height. The highlight is the 13th-century lavabo, a two-storey octagonal washing house where the monks cleaned up before meals. The grounds are free; the small visitor centre with an exhibition and guided tours opens in summer (April to early October in 2026). It is 10 kilometres north-west of Drogheda, off the R168.