Diego Sanchez (born December 31, 1981) is an American professional mixed martial artist. He competes in the Welterweight division. A professional competitor since 2002, Sanchez is most known for his time in the Ultimate Fighting Championship (UFC), where he won the Middleweight tournament of The Ultimate Fighter 1. He has also formerly competed for King of the Cage, where he was the Welterweight Champion.

Sanchez has been involved in more "Fight of the Year" bouts than any other fighter in mixed martial arts; his first was against Karo Parisyan at UFC Fight Night 6, and then again against Clay Guida at The Ultimate Fighter 9 Finale (which culminated into a title shot against then-UFC Lightweight Champion B.J. Penn, where the two headlined UFC 107), and finally against Gilbert Melendez at UFC 166.

Sanchez is one of two fighters to have competed in four different weight classes in the UFC: Middleweight, Welterweight, Lightweight, and Featherweight; the other being Kenny Florian.