Frank Shamrock (born Frank Alisio Juarez III; December 8, 1972) is an American former professional mixed martial artist. Shamrock was the first to hold the UFC Middleweight Championship (later renamed the UFC Light Heavyweight Championship) and retired a four-time defending undefeated champion. Shamrock was the No. 1 ranked pound for pound UFC fighter in the world during his reign as the UFC Middleweight Champion. Shamrock has won numerous titles in other martial arts organizations, including the interim King of Pancrase title, the WEC Light Heavyweight Championship and the Strikeforce Middleweight Championship. Shamrock is widely regarded as one of the greatest mixed martial artists of all time, as well as one of the first complete mixed martial artists, adapting his game from a grounded style of fighting to a more complete, well-rounded, and versatile style that included always improving striking to go along with his skilled ground game.He was named "Fighter of the Decade" for the 1990s by the Wrestling Observer, "Best Full Contact Fighter" by Black Belt magazine (1998), and three time "Fighter of the Year" by Full Contact Fighter Magazine. He is a Seventh degree black belt in submission fighting, awarded by O-Sensei Philip S. Porter of the United States Martial Arts Association. He is the adopted brother of Ken Shamrock.

An author, entrepreneur, philanthropist and social activist, he also was a color commentator for Showtime Networks, Bellator MMA, Glory Kickboxing and Combate America's. Frank has been a brand spokesman for Strikeforce, VAS, UFC, and K-1 MMA and has advised on over 4.5 billion dollars in assets.

After retiring from MMA competition Shamrock retired in Southern California close to his place of birth and extended family.