John Stuart was the son of John, 3rd. Earl of Bute and Lady Mary Wortley-Montagu. He was born in 1744 and succeeded his father in 1792. In 1794 he also succeeded his mother as Baron Mount Stuart. In 1796 he was created 1st Marquess of Bute. He married Charlotte Jane, daughter and co-heir of the 2nd. Viscount Windsor. He died in Geneva in 1814 and was succeeded by his grandson John.