Following the refreshing of its lists, many fighters have shot up the rankings, whilst others have dropped away from potential title shots. 

We take a look at the biggest winners and losers of the WBO’s rankings for May. 

Winners 

Chris Billam-Smith 

Mark Robinson/Matchroom Boxing

Chris Billam-Smith's stock has risen after defeating American cruiserweight Brandon Glanton at the end of April, with the Brit fourth with both the WBC and WBA. 

But it is with the WBO where he is now ranked highest, with the organisation elevating him from fourth to first.  

It was winning the WBO belt that made Billam-Smith a world champion in 2023, and the Bournemouth fighter defended his title twice before losing it to current holder Gilberto Ramirez. 

Highly ranked across all four organisations, Billam-Smith appears to be back in title contention six months after losing his world champion status. 

Ryan Garner 

Leigh Dawney Photography

Chris Billam-Smith's old haunt, the Bournemouth International Centre, appears to have a new star to fill its seats.  

Fresh off the back of a sellout in March, Ryan Garner returns there in July for all-British clash with Reece Bellotti at super featherweight. 

EBU European champion, Garner has entered the WBO’s rankings at number 10. Unbeaten in his 17 professional bouts, Garner’s hopes of a shot at a world title have been bolstered by his entry into the WBO’s top 10. 

Moses Itauma 

Shortly after Moses Itauma’s brutal second-round knockout of Mike Balogun on Saturday night, WBO president Gustabo Olivieri took to Twitter to confirm his status as the organisation’s number one at heavyweight. 

Olivieri wrote: “Moses Itauma has climbed the WBO rankings with talent, discipline, and electrifying performances. Now the #1 world-rated heavyweight contender, his moment is approaching. It’s only a matter of time before he gets his shot and the world sees a new star emerge.” 

Despite the 20-year-old's number one status, Olivieri confirmed that Joseph Parker remains the WBO’s mandatory challenger for reigning champion Oleksandr Usyk. 

He added: “For the record: While Moses Itauma holds the WBO’s #1 world ranking in the heavyweight division, this alone does not confer mandatory status. That designation requires defeating top-rated contender(s). Joe Parker remains the official mandatory and retains priority, per WBO rules.” 

Losers 

Christian M’Billi 

French fighter Christian M’Billi’s inactivity has cost him his spot as the second-best super middleweight in the eyes of the WBO. 

The 30-year-old remains unbeaten in 28 professional bouts, but has not fought since August 2024. M’Billi is set to return to action this summer, facing Maciej Sulęcki in Canada on Saturday, June 27. 

Whoever wins that bout will receive the WBC’s interim super middleweight title, with the full title held by Saúl 'Canelo' Álvarez, the undisputed champion that also holds the WBO, WBA, and IBF titles. 

Arnold Barboza Jr 

(Mark Robinson Matchroom Boxing)

Arnold Barboza Jr has enjoyed a long relationship with the WBO, working his way up their ratings in the super lightweight division. In 2020, he earned the WBO international belt, before moving on to the organisation’s inter-continental belt.  

Victory over Jack Catterall in February saw Barboza Jr pick up the interim world title, teeing up a bout with reigning WBO champion Teofimo Lopez.  

Number one with the organisation before becoming interim champion, Barboza’s defeat to Lopez at the start of May has seen the American tumble to fifth in the WBO’s super lightweight ratings.