The 33-year-old star joined the Royal Marines, the British equivalent of U.S. Navy Seals, and members of the public to take part in the Royal Marine Commando Challenge, a 6.2 mile (10 kilometre) charity race in Devon, England.
The exhausting event raises money for the Devon Air Ambulance and The Royal Marines Charity.
Henry was left flat out after completing the course on Devon's Woodbury Common, which is the same one used by the Marines for their intensive training.
It features tunnels, pipes, wading pools and an underwater section called the sheep dip, which even well trained Marines have been known to struggle to complete.
In an interview posted on Twitter by user @HenryCavillNews, Henry said, "I have to say I was expecting the assault course portion to be a really good section of just getting my breath back after the run but it was the hardest bit."
Henry, whose brother is a Lieutenant Colonel in the Marines, is an ambassador for The Royal Marines Charity, an organisation which helps special forces veterans.
Speaking about his work as an ambassador for the charity he added, "To be an ambassador is for me more of an honour than anything else, it's something which makes me feel special because I have the opportunity to be that one step closer to them, because they are extraordinary individuals."
Obstacle course challenges aren’t the only reason the star has had to stay in shape recently; he’s just wrapped up filming superhero movie Justice League, which will see him return to screens as Superman next year (17).