Jan Thieullier (active in the early 17th century) was a Flemish poet, residing in Mechelen, about whom very little is known.
[1] In January 1617 he was dean of the Mechelen chamber of rhetoric the Peoene (the Peony).
As dean of the Peoene Thieullier was one of the organisers of the blazoenfeest (a rhetoric competition) hosted in Mechelen on 3 May 1620.
As part of the event, a play was performed which Thieullier had written for the occasion: Porphyre en Cyprine.
Thieullier also wrote commendatory verses for Richard Verstegan's Neder-Duytsche Epigrammen (Mechelen, Henry Jaye, 1617) and for Willem van Nieuwelandt's Claudius Domitius Nero (1618) and Poema vanden mensch (1621).