Capel Island (Gaeilge: Oileán an Cháplaigh) is a small island in County Cork, Ireland located a short distance from Knockadoon Head, near Youghal.
Capel Island and Knockadoon Head were legally protected as a national nature reserve by the Irish government in 1985. Most of the reserve, , is owned by the state, with a small part in private ownership . The reserve includes Capel Island, Knockadoon Head and the area of sea between.
The tower on the island is an incomplete 19th century lighthouse. The island is home to a herd of goats.
A story is told of how the island got its name. There was a swimming race to reach the island for ownership. As one man was about to touch land the other reached forth his sword and pipped him at the post. A name associated with this story is De Capel Brookes.
Permission from BirdWatch Ireland is required in order to land on the island.