Minister Pius Thicknesse was a wizard and a Ministry of Magic official in the mid to late 1990s. During the Second Wizarding War, he became Head of the Department of Magical Law Enforcement as well as, later in the War, Minister for Magic under Lord Voldemort's puppet regime while under the Imperius Curse and thus essentially Voldemort's puppet himself. He technically replaced Rufus Scrimgeour as Minister of Magic, who had been murdered by Voldemort. Thicknesse took part in the final conflict of the War where he fought alongside the Death Eaters, still under their curse.
He was ousted from power after Voldemort's defeat and was succeeded by Kingsley Shacklebolt in his post of Minister for Magic.