There has been a shakeup in MMA's rankings with two UFC titles on the line, as well as many other top competitors in action.

Jon Jones defended his light-heavyweight title successfully against Vitor Belfort, while Demetrious Johnson won the first-ever flyweight title. In addition to that, guys like Stefan Struve and Dan Hardy moved up the ladder in their respective divisions.

Here are the pound-for-pound rankings of MMA.

These rankings are the combined efforts of some of Bleacher Report MMA's best writers, as we continue to try to provide you with the best content on the web. For the latest MMA news and freshest MMA opinions, follow them on Twitter:

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Scott Harris https://twitter.com/scottharrismma

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Hunter Homistek https://twitter.com/HunterAHomistek

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Andrew Saunders https://twitter.com/SaundersMMA

Promotion: UFC 

Record: 18-3  

Most Recent Fight: Knockout win over Ryan Bader  

Next Fight: Possibly Dan Henderson 

Previous Ranking: 18 

Lyoto Machida leads off the pound-for-pound rankings, as the 205-pound Brazilian is one of the top guys in the light-heavyweight division.

It's unknown if he will fight again in 2012, but he could fight in early 2013 if Dan Henderson's knee heals up quickly.

Promotion: UFC 

Record: 12-1 

Most Recent Fight: Knockout win over Cody McKenzie

Next Fight: N/A  

Previous Ranking: 23 

Chad Mendes is a top guy in the featherweight division, but needs a couple fights to get back into contention for the title. His crippling body shot over the always tough Cody McKenzie was a step in the right direction.

He needs to get his legal issues cleared up before he fights again, but don't be surprised to see Mendes jump in the rankings with a win in his next bout.

Promotion: UFC 

Record: 20-5  

Most Recent Fight: Knockout win over Jake Ellenberger   

Next Fight: vs. Johny Hendricks at UFC 154

Previous Ranking: 25

Denmark's Martin Kampmann is in line for a title shot in the welterweight division, should he get by fellow contender Johny Hendricks. Kampmann is one of the most resilient men in mixed martial arts and has a cult following due to his toughness.

He is highly skilled and always overlooked. A win over Hendricks would definitely push him further up the rankings. 

Promotion: UFC 

Record: 9-0  

Most Recent Fight: Knockout win over Mark Munoz   

Next Fight: vs. Tim Boetsch at UFC 155  

Previous Ranking: N/A

One of the brightest young fighters in MMA, Chris Weidman has propelled up the rankings with just nine fights under his professional belt.

Very well-rounded and under the tutelage of Matt Serra, there are few who match up well against Weidman. Expect him to be a staple of the pound-for-pound rankings for a long time. 

Promotion: UFC 

Record: 26-6  

Most Recent Fight: Decision loss to Renan Barao   

Next Fight: N/A  

Previous Ranking: 20

Urijah Faber is the definition of a pound-for-pound fighter, as he has competed at featherweight and bantamweight in the past couple years.

Faber is a legend and pioneer of the lighter weight classes, but he is still highly skilled. He doesn't have much to prove anymore, but he will anyways. 

Promotion: UFC 

Record: 21-6  

Most Recent Fight: Knockout win over Brandon Vera   

Next Fight: vs. Alexander Gustafsson at UFC on Fox 5 

Previous Ranking: 22

A longtime legend at 205 pounds, Mauricio Rua is still important in the light-heavyweight division. Rua is looking to return to title contention, and a win over next opponent Alexander Gustafsson would definitely put him near the front of the line.

Tune in to UFC on Fox to watch that fight, because it should be a good one.

Promotion: UFC 

Record: 13-1  

Most Recent Fight: Decision win over Josh Koscheck   

Next Fight: vs. Martin Kampmann at UFC 154  

Previous Ranking: 24

Johny Hendricks has a big chance to jump up the rankings in his upcoming endeavors. He first takes on No. 23-ranked pound-for-pounder Martin Kampmann, which could propel him up the rankings in itself.

Should he win that, he has a claim for a title shot, which would be even bigger. Hendricks has an opportunity to make something of himself here. 

Promotion: UFC 

Record: 17-6  

Most Recent Fight: Submission win over Jim Miller at UFC on Fox 3   

Next Fight: vs. Ben Henderson at UFC on Fox 5  

Previous Ranking: 21

Nate Diaz is the current top contender in the lightweight division and has a chance to grab the gold at UFC on Fox in December.

Diaz's rise to the top has been spectacular since returning to lightweight. He owns three impressive wins in that time over the likes of Takanori Gomi, Donald Cerrone and Jim Miller.

Promotion: UFC 

Record: 11-1-1 (1 NC)  

Most Recent Fight: Decision win over Clay Guida  

Next Fight: vs. Joe Lauzon at UFC 155  

Previous Ranking: 16

A former top contender in the lightweight division, Gray Maynard has begun his road back to contention when he beat Clay Guida in a lackluster main event at UFC on FX 4.

He has an opportunity to get his name back in the hat with a win over Joe Lauzon. It looks like a matchup tailor-made for the former Michigan St. wrestler.

Promotion: UFC 

Record: 16-3  

Most Recent Fight: Decision loss to Demetrious Johnson   

Next Fight: N/A  

Previous Ranking: 12

Joseph Benavidez falls down the rankings a little bit, losing his championship aspirations at the hands of Demetrious Johnson this month.

Benavidez is a three-time title challenger at bantamweight and flyweight. One has to think that the shallowness of the flyweight division will earn him another shot should he win a fight or two. 

Promotion: UFC 

Record: 27-12-1  

Most Recent Fight: Knockout loss to Anderson Silva  

Next Fight: vs. Forrest Griffin at UFC 155  

Previous Ranking: 14

Chael Sonnen is switching weight classes after two unsuccessful bids at the middleweight title, but he still has to be considered a top 205er.

Sonnen has a chance at revenge when he meets Forrest Griffin at UFC 155, a man who owns one of the many triangle-choke victories over Sonnen.

Promotion: UFC 

Record: 10-1 

Most Recent Fight: Knockout win over Antonio Silva  

Next Fight: vs. Junior dos Santos at UFC 155  

Previous Ranking: 17 

Former heavyweight champion Cain Velasquez has a chance to jump up the rankings and earn his title back with his next fight against Junior dos Santos. It will be a chance at revenge, as dos Santos knocked him out to take the title.

Promotion: UFC 

Record: 17-2-1  

Most Recent Fight: Decision loss to Jon Jones   

Next Fight: N/A  

Previous Ranking: 13

Former king at 205 pounds Rashad Evans has not been scheduled to fight since his failed attempt to earn the title back against Jon Jones. 

Evans is still one of the best fighters in the world and has a future outside the Octagon. Let's see how the rest of his career goes first, as he has a chance to fight big names in the future.

Promotion: UFC 

Record: 29-8  

Most Recent Fight: Decision win over Mauricio Rua   

Next Fight: Possibly vs. Lyoto Machida  

Previous Ranking: 11

Dan Henderson should have fought for the title recently, but a knee injury stripped him of that opportunity. Henderson is another pound-for-pound fighter, seeing as he has fought at heavyweight, light heavyweight and middleweight.

He is likely one fight away from re-earning a title shot. 

Promotion: UFC 

Record: 29-1 (1 NC) 

Most Recent Fight: Decision win over Urijah Faber   

Next Fight: Likely vs. Dominick Cruz  

Previous Ranking: 10 

Current interim champion of the bantamweight division Renan Barao jumped up the rankings with his recent win over Urijah Faber. The Brazilian has looked unstoppable since joining the Zuffa family.

When Dominick Cruz heals up from his knee injury, they will unite the titles to have one bantamweight champion.

Promotion: UFC 

Record: 16-2-1 

Most Recent Fight: Decision win over Joseph Benavidez   

Next Fight: N/A  

Previous Ranking: 19

Demetrious Johnson has jumped up the rankings by winning the flyweight title this month over Joseph Benavidez. The former bantamweight has proven himself to be the most underrated fighter in MMA.

People won't underrate him anymore now that he is a titleholder. 

Promotion: UFC 

Record: 14-3-1  

Most Recent Fight: Decision loss to Ben Henderson   

Next Fight: N/A  

Previous Ranking: 9 

Frank Edgar is a former lightweight champion that will now be trying his hand at featherweight. The New Jersey native has shown that toughness and technique can get you to the top of the fight game.

I would love to see him fight Jose Aldo next, but it's unsure if he will.

Promotion: UFC 

Record: 28-5  

Most Recent Fight: Decision win over Nick Diaz   

Next Fight: vs. Georges St. Pierre at UFC 154  

Previous Ranking: 8

The current interim champion of the welterweight division has a chance to be the undisputed welterweight champion when he fights Georges St-Pierre at UFC 154.

Carlos Condit is one of the toughest fighters in MMA and will definitely be one of the toughest fights for St-Pierre.

Promotion: UFC 

Record: 17-2  

Most Recent Fight: Decision win over Frankie Edgar   

Next Fight: vs. Nate Diaz at UFC on Fox 5  

Previous Ranking: 7

Lightweight champion Ben Henderson owns two wins over Frankie Edgar, the man from whom Henderson took the title. He faces a whole new challenge when he meets Nate Diaz next.

A win over Diaz would solidify how good he is and possibly put him in the top five.

Promotion: UFC 

Record: 15-1  

Most Recent Fight: Knockout win over Frank Mir   

Next Fight: vs. Cain Velasquez at UFC 155  

Previous Ranking: 6

Junior dos Santos is an unstoppable force in the heavyweight division. He has never really been in trouble in his UFC tenure.

Dos Santos meets Cain Velasquez in his next fight, a man he has knocked out in the past. 

Promotion: UFC 

Record: 19-1  

Most Recent Fight: Decision win over Demetrious Johnson   

Next Fight: Likely vs. Renan Barao   

Previous Ranking: 5

Dominick Cruz is the king of the bantamweight division and has a unique style that is a puzzle to many. Until his knee heals up, Cruz will be on the shelf.

When he comes back, Renan Barao will be his first opponent. That will be a big test for the champ. 

Promotion: UFC 

Record: 21-1  

Most Recent Fight: Knockout win over Chad Mendes   

Next Fight: N/A  

Previous Ranking: 3

Jose Aldo is a beast and comes in at No. 4 in the pound-for-pound rankings. He has beaten every test put in front of him in impressive fashion.

We don't know his next challenger, but Frank Edgar and Erik Koch are at the center of talks. Both fights would be interesting. 

Promotion: UFC 

Record: 22-2  

Most Recent Fight: Decision win over Jake Shields   

Next Fight: vs. Carlos Condit at UFC 154  

Previous Ranking: 4

Georges St-Pierre has been on the shelf for a while, but he finally returns to unify the welterweight titles at UFC 154. We will see how his knee holds up, especially against a guy who has good leg kicks.

Promotion: UFC 

Record: 17-1  

Most Recent Fight: Submission win over Vitor Belfort   

Next Fight: N/A  

Previous Ranking: 2

Light-heavyweight champion Jon Jones is possibly the best fighter to ever grace the division and he is still very young. He has the potential to be No. 1 given time.

His keylock submission of Vitor Belfort this month helped him retain his title. He also overcame adversity during an early armbar attempt. 

Promotion: UFC 

Record: 32-4  

Most Recent Fight: Knockout win over Chael Sonnen   

Next Fight: vs. Stephan Bonnar at UFC 153  

Previous Ranking: 1

Who else would be the best pound-for-pound fighter in the world?

Anderson Silva is a longtime king in the middleweight and P4P rankings in all media outlets. It's no surprise, as he is the most spectacular fighter in MMA history.