Carolus Mulerius (21 February 1601, Harlingen – 13 August 1638, Groningen) was a Dutch Hispanist and grammarian. He was the son of Christina Maria Six (1566-1645) and Nicolaus Mulerius (1564-1630), who is most famous as an astronomer, but at the time was physician of the city of Harlingen. His family moved to Groningen in 1603, to Leeuwarden in 1608, and back to Groningen in 1614, where his father became Professor of Medicine and Greek at the university. His elder brother (1599-1647) became Professor of Physics and Botany at the same university.