Melvin Paul Guillard, Jr. (born March 30, 1983) is an American mixed martial artist (MMA) currently fighting at lightweight for the Ultimate Fighting Championship (UFC). He debuted with the company on The Ultimate Fighter 2 television series, losing in the first welterweight elimination bout to Josh Burkman. Guillard recently received his blue belt in Brazilian Jiu-Jitsu under Ricco Rodriguez.In 2005 Guillard fought the most meaningful fight of his career up to that point, against Roger Huerta. After Guillard took a competitive decision victory, the fight was ruled a no contest after Huerta appealed the commission making an accusation that Guillard was greasing between round.

Guillard later participated the Ultimate Fighter 2, but was eliminated from the competition. Guillard returned at the season finale, defeating Marcus Davis by technical knockout. Fighting again at welterweight, Guillard lost his next fight, against Josh Neer, by triangle choke submission - which surprised many in attendance. Guillard seemed to control the fight until then, opening a large cut on Neer's forehead in the process.

When the lightweight division was reinstated at UFC 58, Guillard began to transition to the lighter weight class. He made his lightweight debut in the UFC at UFC 60, defeating Rick Davis by first round knockout. On September 23, 2006 Guillard fought former WEC lightweight champion Gabe Ruediger, at UFC 63. Guillard won the fight via KO with a body blow.

Guillard lost his fight against Rich Clementi at UFC 79 by rear-naked choke at 4:40 of the first round. Both before and after the bout there was heated trash talking and gesturing by both fighters.

Melvin was slated to fight Spencer Fisher at UFC 90 in Chicago on October 25, 2008, but was replaced by Shannon Gugerty due to a torn ACL.

Guillard fought The Ultimate Fighter 2 winner Joe Stevenson in the main event at UFC Fight Night 9 on April 5 and was defeated by guillotine choke in only 27 seconds after being dropped by a jab from Stevenson. Guillard publicly accused Stevenson of using Human Growth Hormones (HGH), but was later found to have submitted a urine sample positive for cocaine. After the fight, the Nevada State Athletic Commission suspended Guillard for eight months and fined him $2,100.