Nicholas Robert Diaz (born August 2, 1983) is a retired American professional mixed martial artist who was last signed with the Ultimate Fighting Championship (UFC). Since beginning his career in 2001, Diaz has competed in UFC, PRIDE, Strikeforce, EliteXC, World Extreme Cagefighting (WEC), DREAM, and Shooto. He is a former welterweight champion in Strikeforce and WEC, and is the older brother of Nate Diaz.
Diaz, who is of Mexican and English descent, was born and raised in Stockton, California. Diaz attended Tokay High School in Lodi, California, for a year before dropping out. While a freshman, he was a member of the swim team. Diaz began training in karate and aikido from a young age and also participated in wrestling tournaments during his teenage years. He started training in Sambo at the age of 16 under Bulgarian National Sambo Champion Valeri Ignatov. He was promoted to black belt in Brazilian jiu-jitsu by Cesar Gracie on May 8, 2007. Diaz currently teaches Brazilian jiu-jitsu with his brother Nathan in Lodi, California. Both Diaz brothers are advocates for cannabis.