"Arthur Valerian Wellesley died peacefully yesterday at Stratfield Saye Estate, near Basingstoke, surrounded by his family," the spokesman said.
Also known as the Prince of Waterloo, the 99-year-old duke was a descendant of the 1st Duke of Wellington, who defeated Napoleon at the Battle of Waterloo.
Duke Wellesley was born in Rome on July 2, 1915 and attended Eton and New College, Oxford.
He had been a member of the House of Lords from 1972 until 1999.
His death comes six months before the 200th anniversary of the Battle of Waterloo.
A private family funeral will be held at Stratfield Saye Church on January 8, the spokesman said.