Floyd Mayweather was stripped by the World Boxing Organization of the welterweight world title he won by beating Manny Pacquiao two months ago.
Mayweather had failed to meet the deadline last Friday for paying the $200,000 sanctioning fee required by the WBO after he took the belt from Pacquiao on May 2 in Las Vegas in the richest fight of all time, earning a reported $220 million in the process.
WBO rules require boxers to pay 3 percent of their purse to fight for a world title up to a maximum of $200,000.
The rules also prohibit WBO champions to hold any belts in any other weight divisions. Mayweather is currently also the WBC and WBA champion at junior middleweight (154lb), as well as at welterweight (147lb).
A statement on the Puerto Rico-based sanctioning body's website confirmed that Mayweather, regarded as the best pound-for-pound boxer in the world, was no longer the WBO champion.
"Mr. Mayweather, Jr. failed to pay the $200,000.000 fee required of him as a participant of a WBO World Championship Contest," said the statement.
"Despite affording Mr. Mayweather Jr. the courtesy of an extension to advise us of his position within the WBO Welterweight Division and to vacate the two 154-pound world titles he holds, the WBO World Championship Committee received no response from him or his legal representatives on this matter.
"The WBO World Championship Committee is allowed no other alternative but to cease to recognize Mr. Floyd Mayweather, Jr. as the WBO Welterweight Champion of the World and vacate his title."
After Mayweather (48-0, 26 KOs) defeated Pacquiao to unify three of the four major welterweight world titles, he had declared that would vacate all his titles in order to give younger fighters the chance to win belts.
"I don't know if it will be Monday or maybe a couple weeks," Mayweather said at the post-fight news conference.
"I'll talk to my team and see what we need to do. Other fighters need a chance."
American Timothy Bradley, who defeated countryman Jessie Vargas for the WBO interim welterweight belt on June 27, is now expected to be formally elevated to full champion status by the WBO.