(b. 1562, Troyes, d. 1622, Roma)
French engraver and publisher. He was apprenticed to a goldsmith in Troyes in c. 1577. He emigrated to Rome where he is first documented in 1585. He initially worked for the French publishers Claude Duchet (Claudio Duchetti), Lorenzo Vaccari and Marcello Clodio. He subsequently collaborated with Antonio Tempesta on the Vita et miracula Divi Bernardi Clarevalensis Abbatis which was published in 1587.
Thomassin engraved plates after artists from the preceding centuries including Raphael, Parmigianino, Francesco Salviati and Giorgio Vasari. The decision to produce prints after these earlier Tuscan and Northern-Italian artists was motivated by Thomassin's involvement with the Sienese art collector and dealer, Giulio Mancini (1559-1630).
Between 1608 and 1612 Jacques Callot was present in Thomassin's workshop, where he was tasked with engraving prints after well known paintings: a commercial practice which offered a steady source of income.