Mayweather claimed the title after he defeated Pacquiao on May 2 in the 'fight of the century' which smashed all financial records for a boxing match including total gross, live gate, pay-per-view subscriptions, foreign TV sales and sponsorships.
The WBO asked Mayweather to pay a $200,000 sanctioning fee for the Pacquiao fight and vacate two junior middleweight titles he holds by Friday July 3.
With Mayweather not complying with the requests, the WBO released this resolution statement:
"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 for failing to comply with our WBO regulations of world championship contests.
"The WBO has the utmost respect for Floyd Mayweather Jr. and all that he has accomplished during his storied career.
"Mr. Mayweather has always agreed with and understood that world championships have both privileges and responsibilities and that status as WBO champion is subject to and conditioned on compliance with the WBO rules and regulations."
The Mayweather camp showed their anger at the WBO's ruling.
"It's a complete disgrace," Mayweather Promotions CEO Leonard Ellerbe told ESPN.com.
"Floyd will decide what, or if any, actions he will take. But in the meantime he's enjoying a couple of hundred million he made from his last outing and this has zero impact on anything he does.
"Floyd Mayweather has a great deal of respect for each and every organization, as he has always had in his 19-year career, but he will not be dictated to by any organization or person as it relates to his decision making."