Willem Vrolik (29 April 1801 – 22 December 1863) was a Dutch anatomist and pathologist who was a native of Amsterdam. He was a pioneer in the field of vertebrate teratology. He studied medicine at the University of Utrecht, and furthered his studies in Paris, where he received his degree in 1823. In 1829 he became a professor of anatomy and physiology at the University of Groningen, and in 1831 a professor of anatomy, physiology and natural sciences at the Athenaeum Illustre (University of Amsterdam), where he remained for the rest of his career.