Baron Southampton, of Southampton in the County of Southampton, is a title in the Peerage of Great Britain. It was created in 1780 for the soldier and politician Charles FitzRoy. He was the third son of Lord Augustus FitzRoy, second son of Charles FitzRoy, 2nd Duke of Grafton, while Prime Minister Augustus FitzRoy, 3rd Duke of Grafton was his elder brother. Lord Southampton was also the great-great-grandson (through an illegitimate line) of King Charles II by his mistress Barbara Palmer, 1st Duchess of Cleveland. The Southampton title had previously been created for Charles FitzRoy, eldest natural son of Charles II and the Duchess of Cleveland and the elder brother of Henry FitzRoy, 1st Duke of Grafton, but had become extinct in 1774 on the death of his son William FitzRoy, 3rd Duke of Cle