BJ Penn is one of the greatest fighters to ever step into the Octagon.
He has been a dominant figure in mixed martial arts for a decade and is one of only two fighters to capture UFC championships in two separate weight divisions.
Over the years, Penn has spoiled us all with many exciting and competitive fights.
Today, we take a look back at the best of BJ's fights, both in terms of how exciting they were and how significant they were to Penn's career.
Let's get started...
BJ Penn's third fight with Matt Hughes was important for a couple reasons.
First, Penn and Hughes were 1-1 at this point, and BJ wanted to prove that he was the better fighter.
Second, BJ was coming off of back to back losses the current UFC lightweight champion Frankie Edgar. He needed this win to get himself back on track.
Penn managed to get his career back on track and settle the score with Hughes simultaneously by knocking out the welterweight legend in just 21 seconds.
Some people might disagree with having this fight on the list because it was not Penn's most exciting bout, but I believe the significance of it is enough for it to be here.
BJ has made it known that he wants to earn another shot at the welterweight title.
That fight would be a tough sell because Penn was thoroughly dominated by the current UFC welterweight champion, Georges St-Pierre, last time the two met.
The reason GSP was able to handle BJ so easily was his superior wrestling.
In order to get a rematch with Georges, Penn needed to show that his grappling ability had improved significantly, and he showed that it had definitely improved when he fought Jon Fitch.
Penn managed to win the first round against Jon using his grappling ability, and he arguably could have been given the second round as well.
The fight went to a draw, so Penn did not receive a title shot, but he did succeed in showing us how another fight with St-Pierre might go differently, and that's an important step towards getting another crack at the belt.
His second fight with Frankie Edgar was humbling for BJ.
He had already lost the title to Edgar when the two met for the first time at UFC 112, but the decision was controversial, and many thought that Penn should have retained the belt.
Going into the second fight, BJ didn't seem to show a lot of respect for Frankie and acted like Edgar was lucky to have won the first fight.
It seemed pretty clear that Penn underestimated Frankie and, as a result, was not as prepared for the fight as he should have been.
Edgar won the second fight, again by unanimous decision, but this time, there was no controversy around the decision.
Frankie walked out of UFC 118 with the lightweight belt, and Penn walked out having learned a valuable lesson about never underestimating your opponent.
Another humbling fight for Penn.
BJ and Georges St-Pierre fought for the first time at UFC 58, and it was an extremely competitive fight.
GSP walked away with the split-decision victory, but many thought that Penn also could have been awarded the decision.
When the two met again, it was obvious which fighter had improved the most.
St-Pierre dominated the second fight and won by fourth round TKO (corner stoppage).
This was a very entertaining fight to watch and showed BJ he needed to step up his grappling to compete with larger opponents.
BJ Penn's first title defense after winning the lightweight belt was against Sean Sherk.
A champion's most important fight is their first title defense because it shows the world that they really do deserve their belt.
Penn was wildly successful in his first title defense, out-boxing Sean Sherk for four rounds en route to a TKO victory.
The win was also important for BJ because Sean was a former lightweight champion and was stripped of his title; no one actually beat him.
So, apart from the title being on the line, this fight was to determine who the real king of the division was.
Penn's fight with Kenny Florian was important because it was his first fight after being dominated by Georges St-Pierre.
Before his second fight with GSP, Penn had an aura of invulnerability surrounding him. He had been so dominant in his past three fights that people believed no one in the lightweight division would be able to provide BJ with a challenge.
Then after the loss to St-Pierre, Penn's superman aura was significantly diminished.
In order to get that aura back, BJ needed to make a big statement in his return to the lightweight division.
Penn made that statement by thoroughly outclassing Florian everywhere the fight went and eventually submitting him with a rear-naked choke in the fourth round.
Arguably the most important fight of a mixed martial artists career is their first loss.
Penn's first loss came in his fourth professional fight at the hands of Jens Pulver. The UFC lightweight belt was on the line.
It was a close fight, and BJ did well in the early going, but Jens rallied back in the later rounds and pulled out the decision.
A fighter's first loss is important because it's a tough thing to get over mentally and how the fighter bounces back tells you a lot about what kind of competitor they are.
Penn took the loss in stride and came back even better. BJ would go unbeaten for the next two years and capture the UFC welterweight championship during that stretch.
At the Ultimate Fighter 5 Finale, Penn got a chance to avenge his loss to Jens and capitalized on it, big time.
This victory was gigantic for BJ because it showed how much he had improved since the first fight.
Watching the second fight, you would never have guessed that these two were once in a competitive fight.
Penn schooled Jens, taking him down and working his superior jiu-jitsu.
Pulver held out for as long as he could and managed to escape some close submission attempts, but ultimately succumbed to a rear-naked choke in the first round.
Not only did this fight showcase BJ's improvement, it earned him another shot at the lightweight belt.
Penn fought Matt Hughes for the first time at UFC 46 with the welterweight championship on the line.
Most people thought that BJ didn't have a chance in a fight with Hughes, who was the larger competitor and a dominant champion.
However, technique triumphed over size that night, and BJ won the fight via first round rear-naked choke after rocking the champ with a huge right hand.
It was one of the biggest upsets in UFC history and the first time Penn won a UFC championship.
BJ Penn and Joe Stevenson met at UFC 80, and it was arguably the most dominant performance of his career.
Penn dominated all areas of the fight and shut down all Stevenson's attempts at offense.
BJ opened up a big cut on Joe's forehead in the first round of the fight, and the bout almost had to be called because of the blood getting into Stevenson's eyes.
Joe made it into the second round, but his fortunes didn't improve any, as Penn eventually sunk in the rear-naked choke to end the fight.
This was BJ's most important fight for a few reasons: It was arguably his most dominant performance, he won the UFC's lightweight belt and he became the second fighter in UFC history to capture championships in two weight classes.