John C. Baez is an American mathematical physicist and a professor of mathematics at the University of California, Riverside (UCR) in Riverside, California. He has worked on spin foams in loop quantum gravity, applications of higher categories to physics, and applied category theory.

Baez is also the author of This Week’s Finds in Mathematical Physics, an irregular column on the internet featuring mathematical exposition and criticism. He started This Week’s Finds in 1993 for the Usenet community, and it now has a following in its new form, the blog “Azimuth”. This Week’s Finds anticipated the concept of a personal weblog. Additionally, Baez is known on the World Wide Web as the author of the crackpot index.