Deiveson Figueiredo cannot win the flyweight championship at UFC Fight Night 169 on Saturday against Joseph Benavidez after missing weight.
ESPN's Brett Okamoto reported the Brazilian weighed in at 127.5 pounds on Friday, which is two pounds over the weight limit.
Benavidez can still win the title if he beats Figueiredo. The 35-year-old successfully made weight at 124.5.
The Phoenix-born fighter will also take home 30 per cent of Figueiredo's purse for the headline fight at the Chartway Arena in Norfolk, Virginia.
Okamoto tweeted there could now be serious ramifications for the division:
Brett Okamoto @bokamotoESPN
This is pure speculation, but definitely wonder if the flyweight division will survive if Deiveson Figueiredo wins this fight. The title would still be vacant. Unreal, really. Cejudo saves it. Now Joe B has to save it. And a flyweight (Figueiredo) is actually trying to kill it.
Figueiredo holds a record of 17-1, and was a strong contender to succeed as the new champion after Henry Cejudo vacated the belt.
The UFC has decided to continue the division after considering scrapping the title when Cejudo opted to concentrate on bantamweight, per Okamoto.
Figueiredo will become just the third fighter in UFC history to miss the weight for a title fight and still compete in the bout.
Saturday's clash in the Octagon will be Benavidez's third attempt at winning a UFC championship after losing twice to Demetrious Johnson.
Benavidez, at 28-5, has continued to show excellent form since his earlier title-attempt failures, and he will hope his opponent is affected after losing the chance of becoming the new champion.