B.J. Penn is only the second fighter to have held a UFC title in two different weight divisions.
In 2004, at UFC 46, Penn upset welterweight champion Matt Hughes with a first-round submission to capture his first title. Penn then left the UFC for various reasons and never defended the title.
Penn then came back to the UFC in 2006, but lost his first two fights against Georges St. Pierre and Matt Hughes in the welterweight division.
The UFC offered Penn a role on the fifth season of "The Ultimate Fighter" opposite his old nemesis, Jens Pulver.
Penn would move down to his more natural weight class at lightweight for the opportunity.
Penn easily disposed of Pulver with a second-round submission, and was awarded a shot at the UFC lightweight title.
Because lightweight champion Sean Sherk had recently been stripped of his belt due to a positive steroid test, Penn and Joe Stevenson were set to fight for the vacant title.
In what turned out to be one of the bloodiest fights in UFC history, Penn battered Stevenson before submitting him in the second round.
In his first defense, Penn took on former lightweight champ Sherk in a fight to establish the true champion since Sherk had never lost his title in the ring.
Most had figured the fight would turn into a grappling match, but Sherk was content to box with the bigger Penn.
Penn controlled the fight with his educated jab and in the closing seconds of the third round, knocked Sherk out with a knee to the face.
Penn then went on to defend his title against top contenders Kenny Florian and Diego Sanchez, with neither fight going the distance.
In April, Penn lost his lightweight title to Frankie Edgar in what many are calling the worst decision of the year. Penn looked flat and tired throughout the fight, but seemed to still do enough to win at least three of the rounds.
Still, the judges saw it different and Penn will now rematch Edgar in August in an attempt to regain his title.
Final report: Champ in two weight classes with three defenses of lightweight title.