Earl of Portsmouth is a title in the Peerage of Great Britain. It was created in 1743 for John Wallop, 1st Viscount Lymington, who had previously represented Hampshire in the House of Commons. He had already been created Baron Wallop, of Farleigh Wallop in Hampshire in the County of Southampton, and Viscount Lymington, in 1720, also in the Peerage of Great Britain. The third Earl declared himself King of Hampshire and his brother had him declared insane. The fifth Earl resumed, without Royal licence, the family surname and arms of Wallop.