Daniel Mazia (December 18, 1912 in Scranton, Pennsylvania – June 9, 1996 in Monterey, California) was an American cell biologist, best known for his 1951 research with Katsuma Dan that isolated the cell structures responsible for mitosis.

Mazia grew up in a Jewish family in Philadelphia. He earned a bachelor's degree in 1933 and a Ph.D. in 1937 from the University of Pennsylvania. In 1937-38, he was a National Research Council fellow at Princeton University and at the Marine Biological Laboratory at Woods Hole, Massachusetts. He then joined the zoology faculty of the University of Missouri, where he taught until 1950. From 1951 until his retirement in 1979, he was a professor of zoology at the University of California, Berkeley. After leaving Berkeley until his death in 1996, Mazia was an emeritus professor at Stanford University.

Mazia was a member of the National Academy of Sciences and a fellow of the American Academy of Arts and Sciences. He was awarded the E. B. Wilson Medal in 1981 for his contributions to cell biology.