"Mighty Mouse" is calling it a career.

MMA legend Demetrious Johnson announced his retirement Friday at a ONE Championship event in Denver, ending one of the greatest MMA careers of all time.

The 38-year-old last fought in May 2023. He retires with a pro record of 25-4-1.

Widely considered the greatest flyweight ever, Johnson was the inaugural UFC flyweight champion and defended that belt a record 11 consecutive times before losing to Henry Cejudo in 2018. He made his debut with ONE in March 2019 after being traded to the Asia-based promotion by the UFC in exchange for Ben Askren in a historic deal.

Johnson's only ONE loss came against Adriano Moraes in 2021. However, he got his revenge and beat Moraes on two occasions. By defeating Moraes for a second time, Johnson joined a select list of fighters who defended titles in two major promotions (UFC and ONE).

ONE CEO Chatri Sityodtong announced Friday that Johnson will be the first inductee into the promotion's Hall of Fame, according to Ariel Helwani of Yahoo Sports.

Johnson originally teased his retirement by telling theScore in April 2023 that his trilogy bout against Moraes in May of that year could be his last pro appearance in MMA. The legendary flyweight holds essentially every major record in the UFC flyweight division.