The WWE Hall of Fame member was 79.
"A true trailblazer of the industry, Patterson was linked to many 'firsts' in sports-entertainment throughout his storied career," World Wrestling Entertainment said in a statement. "In a career spanning six decades, the renaissance man left an indelible mark on the industry in the ring, on the microphone and behind the scenes."
Pro wrestler John Cena said he'll never forget Patterson's friendly demeanor and zest for life.
"Pat Patterson lived life as it should be lived with passion, love and purpose," Cena said in a statement. "He helped so many and always entertained with a story or joke. He will live on in my life always. Love you Patrick."
Hossein Khosrow Ali Vaziri, better known as The Iron Sheik, tweeted an all-caps eulogy of his contemporary, lauding Patteron's "beautiful mind for this business and beautiful heart for this world."
"I don't know what to say other than I love you," he wrote. "My heart is broken. God bless you and your family. Thank you for your friendship."
Long-time WWE referee Charles Robinson said he'll miss seeing his old friend in the ring, backstage, on press row and even at the karaoke bar.
"One of the greatest minds in the business and just an all around great guy," Robinson said. "I will miss him and his karaoke! RIP my friend. You are a hero to many!"
The teenaged Patterson was thrown out of his home in Montreal after coming out to his parents and did the unthinkable — immigrated to America to make it in the hyper-macho world of pro wrestling, he wrote in his 2016 biography, "Accepted: How the First Gay Superstar Changed WWE."
He was the first to hold the title of "Intercontinental Champion" in 1979, and his early 80s rivalry with Sgt. Slaughter took pro wrestling to new heights of popularity.
It culminated in the famed "Alley Fight at Madison Square Garden" in New York City on May 4, 1981.
In the 1990s “Attitude Era” of the sport, Patterson was paired with fellow Hall of Fame member Gerald Brisco, performing as CEO McMahon's "stooges."
In various storylines, they’d interfere in matches not involving them and pull other unsportsmanlike hijinks, often in conflict with the era’s prime protagonist “Stone Cold” Steve Austin.
After retiring as a performer, Patterson served as a color commentator and worked behind the scenes in a long career that "helped lay the foundation" of today's WWE, according to McMahon.
"Pat Patterson was more than the first Intercontinental Champion & father of the Royal Rumble Match," McMahon said in a statement on Wednesday.
"He helped lay the foundation for WWE as we know it. His mentorship shaped careers, his creativity sparked innovation and his friendship lifted spirits. Love you, Pat. We miss you."
Cyd Zeigler, co-founder of Outsports.com, said the impact of Patterson's career cannot be understated.
"Having a gay man with a seat at the decision-making table at a company like the WWE was and is incredibly important," Zeigler said.
"While he wasn't out publicly, he was there helping make key creative decisions that were piped into TV sets across America. The visibility of his coming out years later was great, but having a seat at the table and making sure the people around him knew he was gay, the power of that can't be overstated."