#4 Frank Shamrock
One Reign
Four Defences
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Frank Shamrock debuted in UFC on December 21, 1997 at UFC Japan and won the Middleweight Championship (which was later rechristened the Light-Heavyweight belt) in his very first UFC encounter.
Shamrock then went on to become the premier fighter in the company as he successfully defended the title four times in impressive defenses versus top contenders Jeremy Horn and future Light-Heavyweight legend, Tito Ortiz.
His bout with Ortiz at UFC 22 was the 1999 fight of the year, as the pair traded blows for four rounds before Shamrock finally earned a submission win after barraging his opponent with punches.
However, despite this fact, Shamrock felt that he did not have sufficient competition in UFC and chose to vacate the title rather than defend it again and left the company.
He retired a year later only to make unspectacular returns in smaller promotions in 2003 and 2006. He would never again return to UFC to reclaim the title he never lost.
Despite his relatively short run in UFC, Shamrock's title reign should be remembered as one of the greatest in the long history of the Championship.