Floyd Mayweather Jr. vs. Juan Manuel Márquez, billed as Number One/Número Uno, was a welterweight professional boxing match which took place on September 19, 2009, at the MGM Grand Arena in Las Vegas between five-division world champion Floyd Mayweather Jr. (39–0, 25 KO) and three-division champion Juan Manuel Márquez (50–4–1, 37 KO).

[5] Juan Manuel Márquez made a guaranteed $3.2 million, as well as an additional $600,000 due to Floyd Mayweather Jr. coming in two pounds over the 144 lbs weight limit.

A Mayweather left hook, however, caught Marquez coming in and put him down midway through the round.

Mayweather continued to show impeccable defensive skills in Round 4 making Marquez miss with most of his shots.

The disparity between the two fighters grew in the 6th as Mayweather began landing a lead right hand that at one point wobbled Marquez, who had begun bleeding from the nose.

Marquez was simply unable to land against the supremely quick Mayweather, who either dodged the attack outright or shoulder rolled it with ease.

The 10th Round continued with much of the same; Mayweather landing the occasional lunging left hand and lead right and Marquez showing desire but not connecting with anything of significance.

The fight was originally scheduled for July 18, 2009 at the MGM Grand arena but was postponed due to a rib injury sustained by Mayweather.

[9] It was later revealed that the contract was changed a few days prior to the weigh in so that Mayweather would be allowed to weigh up to the welterweight limit of 147 lbs while avoiding paying an additional fine to the Nevada State Athletic Commission, in addition to the fine he agreed to pay to Marquez.