Howth Castle and estate lie just outside the village of Howth, County Dublin in Ireland, in the administration of Fingal County Council. The castle was the ancestral home of the line of the St Lawrence family that had held the area since the Norman Invasion of 1180, and held the title of Lord of Howth until circa 1425, the Baron Howth to 1767, then Earl of Howth until 1909. The castle and estate are held since 1909 by their distaff heirs, the Gaisford-St Lawrence family.

Howth is an affluent peninsular village and outer suburb of Dublin, Ireland. The district as a whole occupies the greater part of the peninsula of Howth Head, which forms the northern boundary of Dublin Bay, and includes the island of Ireland's Eye, which holds multiple natural protection designations.