Thomas Mahieu (born between 1515 and 1527 – died after 1588), also known as Thomas Maiolus, was a French courtier and bibliophile with a special interest in decorative bookbindings. Mahieu was advisor and secretary to Henry II of France, personal secretary to Catherine de' Medici from 1549 to 1560, and subsequently Treasurer-General of France.His book collection is considered second only to that of Jean Grolier, who is considered Mahieu's mentor and spiritual father. Mahieu and Grolier used similar Latin ownership inscriptions on their bindings. Mahieu used the Latinized form of his name on bookplates, Maiolus, which for centuries was mistaken for an Italian surname. It was not discovered until 1926 that Maiolus, the otherwise unattested supposed Italian, and Mahieu, the prominent French p