Floyd Mayweather Jr. is undefeated inside the ring, but the boxing superstar took a loss on Wednesday night after Ultimate Fighting Championship superstar Ronda Rousey took the Best Fighter award during the 2015 ESPY Awards in Los Angeles, California.

Mayweather, who improved his perfect record to 48-0 after winning against Manny Pacquiao in May, was considered heavy favorite to get the Best Fighter award again this year, but Rousey took home the honor.

Rousey, who is the reigning UFC women's bantamweight champion, is coming off a submission win against Cat Zingano at UFC 184 in February in a fight that only lasted for 14 seconds. Before the win against Zingano, she defeated Alexa Davis in 16 seconds at UFC 175 in July last year.

Mayweather previously took a shot at Rousey, when he said he does not now who Rousey is. And after defeating Mayweather in the race for the prestigious award on Wednesday, Rousey took the chance to mock the reigning boxing pound-for-pound king.

"I wonder how Floyd feels being beat by a woman for once," Rousey told ESPN announcers as quoted by BoxingScene. "I'd like to see him pretend to not know who I am now."

Aside from the Best Fighter citation, Rousey also bagged the Best Female Athlete award, which could serve as an inspiration for her upcoming title defense next month.

Rousey, who holds a perfect 11-0 record inside the UFC Octagon, will go up against Bethe Correia at UFC 190 on August 1 in Rio de Janeiro, Brazil. The 28-year-old superstar is currently in deep training for the fight, and a popular boxing figure witnessed how Rousey is preparing for her upcoming title defense.

Former world champion Mike Tyson was left in awe when he watched the workout of Rousey at the Glendale Fight Club on Wednesday -- hours before the 2015 ESPY Awards night.

Tyson witnessed how Rousey sparred with training partner Justin Flores. Based on what he saw, Tyson is not surprised why Rousey is considered as the best UFC women's fighter and one of the best pound-for-pound mixed martial artists today.

"Ronda is a lady and she's bright, kind, sweet and adorable. But her whole barometer is, she's the killer," Tyson said of Rousey via Yahoo Sports. "She has that killer aura, meaning anything is capable of happening. Whoa! That's exciting before the fight even starts."

Rousey said that she was surprised when she saw Tyson inside the gym. She said that meeting and getting advice from one of the best boxers in history is huge, but Rousey quickly added that the talk with Tyson will only sink into her after beating Correia next month in Brazil.