Tantallon Castle is a ruined fortress located in East Lothian, Scotland, overlooking the Firth of Forth. It was built in the mid-14th century by William Douglas, the 1st Earl of Douglas, and served as the seat of the Earls of Douglas. The castle underwent several modifications over the centuries, including an expansion in the 15th century by James Douglas, the 9th Earl of Douglas.

Tantallon Castle played a significant role in the Wars of Scottish Independence, withstanding several sieges by English forces. In 1651, during the Third English Civil War, it was besieged by Oliver Cromwell's army and was surrendered after a bombardment by artillery.

The castle features a unique design with a long curtain wall and several towers, including the 30-metre tall Douglas Tower. Visitors can explore the castle ruins, including the Great Hall, the kitchen, and the battery. From the top of the castle walls, visitors can enjoy panoramic views of the surrounding countryside and the sea.

Today, Tantallon Castle is managed by Historic Environment Scotland and is open to the public for guided tours and self-guided exploration. It is a popular tourist destination and has been featured in several films and television shows.