UFC 31, titled "Locked and Loaded," was a mixed martial arts event held by the Ultimate Fighting Championship on May 4, 2001. The event took place at the Trump Taj Mahal in Atlantic City, New Jersey, and was broadcast live on pay- per-view in the United States. The main event was a heavyweight title bout between Randy Couture and Pedro Rizzo. The card also featured a welterweight title bout between Pat Miletich and Carlos Newton. Notable fighters included the first appearance of future UFC Welterweight Champion Matt Serra, the professional debut of future multi-divisional UFC Champion B.J. Penn, and Kevin Randleman's first fight in the Light Heavyweight division. UFC 31 was significant for adopting the then-new Unified Rules of Mixed Martial Arts set by the New Jersey State Athletic Control Board. This event reformed weight classes to what are closer to the current standards. Dana White, UFC president, has praised UFC 31 as one of the best fight cards ever, highlighting the thrilling main event and the bout between Matt Serra and Shonie Carter, which featured an infamous backfist finish. The event included notable awards such as Fight of the Night for Randy Couture vs. Pedro Rizzo, Knockout of the Night for Shonie Carter, and Submission of the Night for Carlos Newton. Overall, UFC 31 is remembered as a landmark event in UFC history for both its fights and the formalization of the sport's rules and weight classes.