He was 63 years old.
"WWE is saddened to learn that Sid Eudy has passed away. WWE extends its condolences to Eudy's family, friends and fans," the wrestling promotion wrote on social media.
In a Facebook post, Eudy's son, Gunnar, explained that his father had battled cancer for several years.
"He was a man of strength, kindness, and love, and his presence will be greatly missed," Gunnar Eudy wrote, thanking those who kept his father in their thoughts and prayers.
Sid's many names
Eudy, born in Arkansas but closely tied with Memphis, Tennessee, broke through in professional wrestling in the late 1980s, competing with regional promotions and at least one overseas company, where he brought his 6-foot-9, 300-pound frame to audiences.
Eudy was most noted for his ring names throughout his career, with fans drawn to three of them: Sid Justice, Sid Vicious, and Sycho Sid - Sid Vicious is not to be confused with the Sex Pistols bassist of the same name.
In 1989, he arrived in World Championship Wrestling with the Sid Vicious character. Two years later, he joined the World Wrestling Federation as Sid Justice.
He had another stint with WCW in 1993, spending just one year with the company. After spending time with the USWA, he rejoined the WWF, which would later be renamed WWE, in 1995 as Sycho Sid, a character billed as intense and unstable. During this run, he earned his first world title.
After WWF released him while recovering from an injury, he bounced around a few promotions before returning to WCW around the turn of the millennium, which was the inspiration for his Millennium Man character. He earned his second and final world title while in the promotion.
A freak leg injury in 2000 forced a retirement, though he would go on to travel independent promotions into the 2010s when Eudy returned to WWE in a one-off appearance in 2012.
Paying tribute
Eudy's contemporaries remembered him in the wake of his passing, with some calling him special and impressive.
"Sid had such a presence. When Sid Vicious stepped through the curtain, you knew you were looking at someone special. He had it all and he looked as impressive as anyone to ever enter the squared circle," former WCW and WWE wrestler Diamond Dallas Page said.
"So very sad to hear of the passing of Sid Eudy. I have nothing but the fondest memories of working with Sid. My thoughts are with his family, friends, and fans," Eric Bischoff, the former head of WCW, said.
"Without Sid Vicious, I don't think my brother and I would have made it to WCW. His impact on this business was undeniable, and he paved the way for so many of us," hall of fame wrestler Booker T. Huffman said.
Eudy is survived by his wife and two sons.