The two are friendly in real life—the actor even attended the Jimmy Kimmel Live! host's 2013 wedding. But on TV, they are arch enemies.
It all began in the early times of the show, which premiered in 2003. Kimmel closed his Jimmy Kimmel Live! shows with, "Apologies to Matt Damon, we ran out of time"—even though he wasn't scheduled to appear. It soon became a recurring gag and led to an epic mock celebrity feud that continues to this day.
More than a week before the 2017 Oscars, when asked about Kimmel's hosting gig, Damon told E! News, "He's gonna be really terrible no matter what."
When asked if he had any message for Kimmel on his hosting skills, Damon joked, "No, [Jimmy] knows I hate him, and there's also a restraining order at the moment, so we're not allowed to directly address each other."
In a 2013 interview with NPR, Kimmel recalled starting the tradition.
"We had a bad show...The guests were bad, and I was feeling pretty bad about myself at the end of the program. And I decided to say, for the amusement of one of our producers who was standing next to me...'I want to apologize to Matt Damon. We ran out of time,'" he said. "And he got a kick out of it, the producer, so I just started doing it every night to amuse him."
"Matt Damon was just the first name that popped into my head. I was trying to think of an A-list star, and somebody we absolutely would not bump if he was on the show," Kimmel said.
Damon finally did appear on Jimmy Kimmel Live! for a primetime special in 2006. Of course, as soon as he sat down on the couch, they...ran out of time.
"When he did a prime-time thing, I went on, and the joke was that he took so long introducing me that by the time I got on, we were out of time," Damon told Parade magazine in 2011. "So we got into a fake fight."
In 2007, Kimmel announced in a mock video segment his sidekick Guillermo would be taking on the role of Jason Bourne in The Bourne Ultimatum. He comes face-to-face with Damon, who says angrily, "Are you from Kimmel? What, now he wants to bump me from my own f--king movies?!"
The Oscar-winning actor famously helped the host win an Emmy, given for the 2008 viral video "I'm [Expletive] Matt Damon," which starred Kimmel's then-girlfriend Sarah Silverman. The clip spurred the reaction video that "I'm [Expletive] Ben Affleck," which featured a slew of celebrities and spoofed "We Are The World."
In 2008, Damon helped Kimmel's show win one of its first Emmys!
Kimmel's girlfriend at the time, Sarah Silverman, and Damon took part in a Jimmy Kimmel Live! music video titled, "I'm F--king Matt Damon." The video went viral and won Outstanding Original Music and Lyrics at the Creative Arts Emmys.
In 2010, Damon got his revenge on Kimmel on Jimmy Kimmel Live!'s post-Oscars special. In a skit called "The Handsome Men's Club," Kimmel gets evicted from a group of actors and Damon tells him "We're all out of time."
Two years later, Damon appeared on the show's post-Oscars special again, this time appearing in a parody trailer titled Movie: The Movie. He appears for a few seconds and is then cut from the film, cursing, "I can't believe I fell for that! F--k Kimmel!"
In 2013, Damon hijacked Jimmy Kimmel Live! and guest-hosted the show, now named Jimmy Kimmel Sucks! The host's parents, Kimmel and other stars appeared on the show. And, of course, Damon takes over the "We ran out of time" joke.
"Tonight, you didn't run out of time for me, did you, Jimmy? No, no I ran out of time for you," Damon says as a bound and gagged Kimmel makes a muffled sound. "What's that Jimmy? Huh? Is there a new host in town? And his initials are M.D. That's right. The doctor is in."
In 2014, Damon returned to Jimmy Kimmel Live! to read "Mean Tweets" but instead of his insult being posted by an anonymous Twitter user, it was written by Kimmel.
He also appeared on the show to join his co-stars from The Monuments Men. But he was made to sit in a toddler-sized chair and when it came time for him to finally speak, the fire alarm went off. Oops!
Months later, Kimmel honored Damon for his 44th birthday by having a child come onstage and wear a cardboard cut-out of Kimmel's vision of "Matt Damon," who, spoiler alert, looks nothing like him.
"Hello, everybody, I'm Matt Damon. Not only was I born, but I was also Bourne—Jason Bourne—I say jokes like these because I'm dumb," the kid said. "I grew up in Cambridge, Massachusetts, with my parents and brother. I wet the bed until I was 19. Well, that's my story, and thank you, Jimmy Kimmel, for finally putting me on your show!"