Killyleagh Castle is a private family residence that is said to be the oldest inhabited castle in Ireland. It has been the home of the Hamilton family since the 17th century Plantation of Ulster and acquired its fairy-tale silhouette in the 1850s when the turrets were added, but it is mostly the same castle that the second Earl of Clanbrassil rebuilt in 1666. The castle hosts occasional concerts. In the past performers have included Van Morrison, Arlo Guthrie, Jackson Browne, Glen Hansard and Bap Kennedy.
It was the birthplace of Sir Hans Sloane, 1st Bt. He began collecting plants and birds' eggs on the shores of Strangford Lough and his accumulation grew into a priceless collection that formed the nucleus of the British Museum. He was also personal physician to King George II and a slave owner.
Killyleagh is the home town of David Healy, the retired Northern Ireland football player. Healy is Northern Ireland's record goalscorer by a considerable distance, with 36 goals. The second highest total is 20 goals. He also holds the record for most goals scored in a European Championship Qualifying Phase, with 13 goals during the country's failed bid to reach Euro 2008. Healy's former Bury teammate Trevor Carson is also from Killyleagh.