-- Check out my rankings within each division by clicking on the links below. If there is a lineal champion in the weight class he is ranked No. 1.
Who is the best fighter regardless of weight class? See ESPN's pound-for-pound rankings.
For a list of the current champions in all weight classes, click here.
Note: Results through Aug. 22. In an effort to provide the most up-to-date rankings, ESPN.com's division-by-division boxing rankings will be updated every Tuesday.
More divisional rankings
WELTERWEIGHT DIVISION (UP TO 147 POUNDS)
1. Keith Thurman (27-0)
The hard-hitting and exciting Thurman made his third title defense in a rousing battle with former titleholder and good pal Shawn Porter on June 25 at Barclays Center in Brooklyn, New York. The fight was the headliner on CBS in prime time -- the network's first prime time card since Muhammad Ali-Leon Spinks I in 1978 -- and Thurman and Porter delivered a tremendous fight of the year candidate, which Thurman, the bigger puncher and better defender, won by close decision, 115-113 on all three scorecards. A rematch is likely, although Thurman said he would prefer a title unification match with Danny Garcia (32-0) first.
2. Kell Brook (36-0)
Brook, who outpointed Shawn Porter to win a belt in August 2014, has made three dominant defenses, knockouts of Jo Jo Dan, Frankie Gavin and woefully undeserving mandatory challenger Kevin Bizier on March 26. Brook did as he pleased and scored two knockdowns en route to a second-round knockout. With the mandatory out of the way, Brook was close to a deal to unify belts against Jessie Vargas in September but when that deal went south Brook and promoter Eddie Hearn pulled a huge surprise -- Brook will move up to middleweight to challenge the fearsome Gennady Golovkin (35-0). Whoa!
Next: Sept. 10 vs. Golovkin
3. Timothy Bradley Jr. (33-2-1)
In his first fight with trainer Teddy Atlas, Bradley looked fantastic as he wiped out an out-of-shape Brandon Rios in a ninth-round knockout victory in November. But Rios is no Manny Pacquiao, so when Bradley and Pacquiao met for the third time on April 9, it was a different story. Bradley got knocked down twice and lost a clear unanimous decision -- 116-110 on all three scorecards -- in what Pacquiao said would be his final fight. Bradley officially is 1-2 against Pacquiao but most of the world agrees he should be 0-3. He can't beat Pacquiao, but he would probably beat most everybody else at 147 pounds.
4. Danny Garcia (32-0)
Garcia vacated his unified junior welterweight belts and moved up to welterweight in August 2015 and mowed down faded former titlist Paulie Malignaggi in nine one-sided rounds. On Jan. 23, Garcia headlined the debut of Premier Boxing Champions on Fox in prime time and although he struggled early against Robert Guerrero, he came on strong in the second half of the fight to win a vacant belt. His first defense is expected to come Oct. 15 against former two-time titleholder Andre Berto (31-4).
5. Amir Khan (31-4)
England's Khan, a former unified junior welterweight titlist, was unable to land fights with either Floyd Mayweather or Manny Pacquiao, who each strongly considered fighting him but went in other directions, so he jumped at the chance to challenge middleweight champion Canelo Alvarez on May 7. Khan, who had won three fights in a row against good opposition since moving up to welterweight (Luis Collazo, Devon Alexander and Chris Algieri), moved up again to meet Alvarez at a catchweight of 155 pounds and while he looked excellent early and gave Alvarez problems with his speed and movement, the more powerful Alvarez eventually connected with a mighty right hand that knocked Khan out cold in the sixth round. Khan said he would return to welterweight, where he can compete with anyone.
6. Shawn Porter (26-2-1)
Porter didn't look so good as he lost a majority decision and his world title to England's Kell Brook in August 2014 but then he won his next two fights, including a big one against former titleholder Adrien Broner, whom he took to school in June 2015. After a year layoff, Porter returned on June 25 to challenge pal and world titleholder Keith Thurman in one of the best matches that could be made in boxing. And they more than lived up to the expectations with a sensational action battle, which Porter lost by the closest of margins, 115-113 on all three scorecards. A rematch figures to happen eventually.
7. Errol Spence Jr. (21-0)
Spence was the best pro prospect from the 2012 U.S. Olympic team. He has lived up to the hype so far in the pros, as he has looked impressive fight in and fight out. Spence, who looks every bit like a future world titleholder, was sensational on April 18 in the main event of a Premier Boxing Champions card on NBC, as he destroyed for junior welterweight titlist Chris Algieri, by far his best opponent. He dropped Algieri three times in a fifth-round knockout win. In his next fight, on Aug. 21, Spence destroyed Italy's Leonard Bundu by brutal sixth-round knockout in a title eliminator to earn a mandatory shot at titleholder Kell Brook (36-0).
8. Jessie Vargas (27-1)
Vargas, a former junior welterweight titleholder, moved up in weight and challenged Timothy Bradley Jr. for a vacant belt in June 2015. Although Vargas lost a unanimous decision, he nearly knocked Bradley out in the final seconds of the fight. Vargas didn't get the rematch he wanted but instead got a chance to face Sadam Ali on March 5 on HBO for the belt Bradley vacated and he made the most of his opportunity. Vargas looked sharp in an impressive ninth-round knockout victory. He was supposed travel to England to fight Kell Brook in a unification match in September but the deal fell apart and he wound up with an even bigger fight -- a high-profile defense against unretiring Manny Pacquiao (58-6-2).
Next: Nov. 5 vs. Pacquiao
9. Lamont Peterson (34-3-1)
Peterson, a former junior welterweight titleholder, has had his last two fights in the welterweight division, although not at the limit of 147 pounds. In April 2015, he lost a close decision to Danny Garcia in a much-anticipated fight that could have gone either way. In October, he was on the winning side of a debatable decision win against 2008 Olympic gold medalist Felix Diaz.
10. Konstantin Ponomarev (30-0)
Russia's Ponomarev has scored very solid wins in two of his past three fights by knocking his opponents from the undefeated ranks. In May 2015, he outpointed Mikael Zewski, a highly regarded up-and-comer who was 26-0 at the time. On April 9, on the Manny Pacquiao-Timothy Bradley III undercard, he won a split decision against Brad Solomon, who was 26-0 at the time, as well. Ponomarev was ordered to face Errol Spence Jr. (20-0) in a title eliminator to get a shot at Kell Brook, but Ponomarev passed on the opportunity because of a hand injury.