The 54-year-old's impressive physique was front and center in last year's "Mission Impossible: Rogue Nation," which featured his Ethan shirtless for a chunk of the film.
This 45-year-old former Calvin Klein model hasn't let himself go. Exhibit A is 2013's "Pain & Gain."
Robert Downey, Jr.
Marvel's marquee star packed on 25 pounds of muscle when he first donned Tony Stark's armor in the first "Iron Man" film, according to Men's Fitness.
Damon, 45, looked fantastic when producer Frank Marshall tweeted this picture from the first day of production on "Jason Bourne."
The action star, pushing 50, has studied Wing Chun, kung fu, karate, and kickboxing, according to TheLADBible. He follows a strict diet and workout regime. Obviously.
The 44-year-old actor spent almost two years getting in shape to become the buffest Batman ever.
At 52, the actor and self-proclaimed adrenaline junkie stays in shape by avoiding alcohol altogether and surfing and skiing, according to the Daily Mail.
The most bad-ass double-0 since Sean Connery spent months with a personal trainer to make himself look like a killing machine, Nerd Fitness reports.
The 44-year-old "30 Seconds to Mars" frontman has been in the same shape since his 20s. How does he do it? Leto put it down to two main factors in his interview with Rolling Stone. “Twenty solid years of eating vegetarian/vegan and taking care of myself,” Leto told the magazine. “It’s probably just down to sleep and diet.”
The 48-year-old former NFL player and "Old Spice" pitchman told bodybuilding.com, "I always stay about two weeks out from being able take my shirt off. There's no off-season for me. I don't like this whole bulking up and getting down thing. You should be ready to look good all the time."
Dwayne "The Rock' Johnson
The actor has perhaps the strictest workout regimen in all of Hollywood.
"I start working out pretty early, around 4 a.m. When I'm filming, I do cardio and I lift before going to set. I train about six days a week, and even when I'm not filming I get up between 3 and 5 a.m. just to train. I love training when the sun is coming up because it allows me to put on my headphones and step off the crazy treadmill that is everyone's life," he told bodybuilding.com
At 61, the Oscar winner is the oldest on this list. He sported impressive arms as he prepared to play Commissioner Gordon in the DC Universe.
The 44-year-old "Wolverine" actor has had an impressive 16-year run as his signature character, and has set the gold standard for physiques in superhero movies.
Honorable mention: The "Magic Mike" star & fitness-book author is just three months shy of turning 40. However, we're confident he'll still be in shape when he faces off against Ben Aflleck's Batman as Deathstroke.