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 May 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
FEATHERWEIGHT DIVISION (UP TO 126 POUNDS)
1. Leo Santa Cruz (33-1-1)
Santa Cruz, a former bantamweight and junior featherweight titlist, claimed a vacant featherweight belt in August 2015 as he outpointed Los Angeles rival Abner Mares in a much-anticipated fight that lived up to its hype. After retaining the title by dominant fifth-round knockout of former junior featherweight titlist Kiko Martinez in an action-packed but one-sided fight, Santa Cruz lost the belt by majority decision to former unified junior featherweight titleholder Carl Frampton in a 2016 fight of the year contender. The Jan. 28 rematch was another exciting and very close fight, but Santa Cruz exacted revenge to reclaim the belt by majority decision. A third fight probably will happen eventually, but not next as Santa Cruz has been ordered to face Mares in a rematch, which is likely for Sept. 9 in Los Angeles on Showtime.
2. Carl Frampton (23-1)
After Northern Ireland's Frampton, the 2016 consensus fighter of the year, traveled to Scott Quigg's turf in England and outpointed him to unify junior featherweight world titles, Frampton moved up in weight and challenged featherweight titleholder Leo Santa Cruz in July. The fight more than lived up to the lofty expectations as they turned in a bona fide fight of the year candidate, which Frampton won by majority decision in a mild upset to become the first fighter from his country to win titles in two weight classes. They met again in the much-anticipated rematch on Jan. 28 and produced another outstanding fight, but this time Santa Cruz got the nod by majority decision. Both fighters said they want a trilogy, but it's unlikely to happen next.
3. Abner Mares (30-2-1)
Mares, who has won world titles in three weight classes, dropped a majority decision to Leo Santa Cruz for a vacant title in a terrific fight in August 2015. After a 16-month layoff because of two fight postponements, Mares returned to outpoint Argentina's hard-charging Jesus Cuellar and take his belt on Dec. 10 in an excellent fight that featured Mares scoring an 11th-round knockdown. Next up, Mares figures to get the rematch he has wanted with Santa Cruz. That fight is on the drawing board for Sept. 9 in Los Angeles and on Showtime.
4. Gary Russell Jr. (28-1)
In June 2014, Vasyl Lomachenko dominated Russell in their fight for a vacant title. After Russell rebounded with a tuneup victory, he challenged Jhonny Gonzalez for his belt in March 2015 and was brilliant. Russell, whose hands might be the fastest in boxing, crushed Gonzalez, dropping him three times en route to a fourth-round knockout victory to win the belt. After 13 months out of the ring, in part because of a cut, Russell returned for his first defense April 16 and smashed Patrick Hyland, whose presence in a world title bout was mystifying. Russell dropped him three times in a second-round knockout. In defense No. 2, Russell looked tremendous in a one-sided seventh-round knockout of interim titlist and mandatory challenger Oscar Escandon on May 20.
5. Oscar Valdez (22-0)
Valdez, Mexico's only two-time Olympic boxer, made his first title defense in impressive fashion, dominating Japanese mandatory challenger Hiroshige Osawa en route to a seventh-round knockout in November on the Manny Pacquiao-Jessie Vargas undercard. Defense No. 2 came against mandatory challenger Miguel Marriaga, a tremendous puncher from Colombia, in the main event of a Top Rank PPV card. It was a terrific fight against a quality opponent. Valdez scored a 10th-round knockdown and won by unanimous decision.
6. Lee Selby (24-1)
Wales' Selby was scheduled to make his mandatory defense against former titlist Jonathan Victor Barros (41-4-1), of Argentina, on Jan. 28 on the Carl Frampton-Leo Santa Cruz II undercard hoping a win will set him up for a unification fight with the main event winner. However, the fight was canceled at the weigh-in because Barros came up positive for hepatitis in his pre-fight medical exam. With his mandatory defense in limbo, Selby returned in a nontitle junior lightweight bout against Spain's Andoni Gago on March 4 and won by ninth-round knockout on the David Haye-Tony Bellew undercard. The fight with Barros will be rescheduled for no later than July 13 after Selby's team won a purse bid.
Next: TBA vs. Barros
7. Jesus Cuellar (28-2)
Argentine slugger Cuellar made his second defense in December 2015 against Puerto Rico's Jonathan Oquendo, whom Cuellar easily outpointed in a snoozer because Oquendo ran for most of the fight. His third defense, against Abner Mares, was scheduled for June but postponed until Dec. 10, when Cuellar got dropped by Mares in the 11th round and lost a split decision and his belt.
8. Scott Quigg (33-1-2)
England's Quigg suffered a broken jaw and lost his junior featherweight belt to Carl Frampton by split decision in their huge unification fight in February 2016. Returning from the injury on Dec. 10, and moving up in weight, Quigg scored a sensational ninth-round knockout of Mexico's Jose Cayetano to announce his arrival at 126 pounds. Quigg, in his first fight with trainer Freddie Roach after parting ways with Joe Gallagher, returned April 29 on the Anthony Joshua-Wladimir Klitschko undercard and claimed a hard-fought unanimous decision against Romania's Viorel Simion in an eliminator to earn a shot against the winner of the impending fight between titlist Lee Selby and Jonathan Victor Barros.
9. Claudio Marrero (22-1)
On April 29, Marrero, a southpaw from the Dominican Republic, won his eighth fight in a row since dropping a competitive decision to former world titleholder Jesus Cuellar in 2013. Marrero knocked out Carlos Zambrano with a clean straight left hand to the chin in the first round. The impressive victory netted Marrero an interim belt.
10. Joseph Diaz Jr. (24-0)
The 2012 U.S. Olympian has steadily been moving up the ladder and could be close to a title opportunity. In his most recent fight, he easily routed previously-undefeated Manuel Avila - 100-90, 99-91, 99-91 - on the May 6 Canelo Alvarez-Julio Cesar Chavez Jr. HBO PPV undercard.