Glenveagh Castle is a 19th-century castellated mansion located in Glenveagh National Park in County Donegal, Ireland. It was built between 1867 and 1873 by John George Adair, a wealthy landowner from County Laois. The castle was designed by John Townsend Trench, who was a leading architect of the time, and was built in a Scottish Baronial style.

The castle is situated on the shores of Lough Veagh, surrounded by lush gardens and rugged mountain landscapes. It was acquired by the Irish government in 1981 and is now open to the public as a museum. Visitors can take a guided tour of the castle, which includes a look at the lavish Victorian interior with original furnishings, tapestries, and artwork.

The surrounding gardens, which were also designed by Trench, cover an area of about 180 hectares and include exotic plants and trees from all over the world, as well as traditional Irish plants. Visitors can stroll through the walled garden, take a walk around the tranquil lake, and admire the stunning views of the Derryveagh Mountains.

Glenveagh Castle is also famous for its connection to the famous musician, Henryk Wieniawski, who was a frequent visitor to the castle. Wieniawski composed some of his most famous works while staying at Glenveagh Castle, and a room in the castle has been dedicated to his memory.