Willem Baudaert or Baudartius (Deinze, Flanders, 13 February 1565 - Zutphen, 15 December 1640), born Willem Baudart, was a Dutch theologian. Baudartius College, a Christian secondary school in Zutphen, is named after him.
Born to Protestant parents in Flanders and a fervent counter-remonstrant, Baudartius left the Netherlands on the arrival of Fernando Álvarez de Toledo and landed in England at Sandwich. He studied at Canterbury as well as on the continent at Ghent, Leiden, Franeker in Heidelberg. He served as a preacher at Kampen (1593), Lisse (1596) and Zutphen.
Highly knowledgeable in Hebrew, he was asked to take part in the Statenvertaling translation of the Bible. He also wrote a collection of spells (Apophthegmata Christiana, ofte gedenckweerdige, leerzame en aerdige spreucken... (1605, 1620) and a pamphlet opposing the Twelve Years' Truce (Morghen-Wecker der vrye Nederlantsche provintien (1610).