From Wikipedia, the free encyclopedia. Frank Shamrock (born Frank Alisio Juarez, III; December 8, 1972) is a retired mixed martial arts fighter. Shamrock was the first to hold the UFC Middleweight Championship (later renamed the UFC Light Heavyweight Championship) and retired as the four-time defending undefeated champion. Shamrock was widely credited as being the #1 ranked pound for pound fighter in the world during his reign as the UFC Middleweight Champion. Shamrock has also won numerous tit...