Castle Sween is one of the oldest remaining castles in Scotland. Dating from the late 12th century, it was built by by Suibhne, anglicised as Sween, when Argyll was not part of the Kingdom of Scotland. He was a chieftain of Irish descent and ancestor of the MacSweens, after which the castle and the adjacent sea loch is named.

The castle was destroyed by Irish confederate forces in 1647 following its part in the Wars of the Three Kingdoms.