Undefeated five-division boxing champion Terence “Bud” Crawford has retired from the sport, he announced Tuesday.

“Walking away as a great with nothing else left to prove. #CrawfordERA,” Crawford, 38, wrote in an Instagram post.

Crawford retires with a 42-0 career record, including 31 wins by knockout. His retirement comes three months after he defeated Canelo Alvarez to become the undisputed super middleweight champion in September.

He is the only boxer to become an undisputed champion in three weight classes, having also done so in the welterweight and junior welterweight divisions.

In total, Crawford won 18 world titles in five weight classes, including lightweight and junior middleweight. The Omaha, Nebraska, native made his professional debut in 2008 and won his first title in 2014, defeating Ricky Burns for the WBO lightweight championship.

“I’ve been blessed to live out a dream that started long before the lights, the fans, or the world titles,” Crawford wrote in the caption of a YouTube video announcing his retirement. “From Omaha to the biggest stages in boxing, every step of this journey was earned through sacrifice, discipline, and faith.

“I gave this sport everything I had. I faced the best, moved through weight classes, and made history on my own terms. 42-0. 3x Undisputed. 5 Division World Champion. No shortcuts. No excuses. This isn’t goodbye to boxing…it’s a thank you.”

Crawford also showed gratitude for the support he’s received from his family and fans throughout his career.

“Thank you to my family, my team, my city, and the fans who rode with me through every chapter,” he wrote. “Thank you to the sport for shaping the man I am today. The gloves may have come off but legacy is forever. History is never retired.”