The photo features Hunnam as his character Henri Charriere, who was arrested for a murder he did not commit.
"He will stop at nothing to reclaim his freedom," a caption on the photo reads. "See Charlie Hunnam as Henri Charrière in [Papillon] in theaters August 24th."
The film tells the real-life story of Charrière, a safecracker who partnered with convicted counterfeiter Louis Dega (played by Rami Malek) to escape the Devil's Island penal colony they were both sentenced to.
Papillon is a remake of a 1973 film of the same name, which starred Steve McQueen and Dustin Hoffman, which was in-turn based on Charrière's autobiography.
Many of Hunnam's fans have been talking about the film on social media, with one saying they "think he will do Steve McQueen proud."
"Read this book in 7th grade. It moved me to the core," another person commented. "Can't wait!"
Just watched the original one with Steve McQueen last night! Love that movie! I hope they can make this one, just as good!— Brian Wood (@wtrucker59) August 5, 2018
Hunnam is best known for portraying Jax Teller on Sons of Anarchy, but he's also starred in films such as The Lost City of Z and 2017's King Arthur: Legend of the Sword.
Regarding what it was like to move on from playing Jax to taking on other roles, Hunnam previously told Glamour that it was not easy task.
"It was actually quite emotional for me, living and loving that guy for eight years, to have to finally put him to bed," he confessed.
"I found myself going back to set a lot. I knew the security guards and for a couple of days said, 'Oh, I forgot something,' so they'd let me onto the set, and I'd just walk around at night because I wanted to be in that environment and go through a personal process of saying goodbye," Hunnam added. "After a couple of nights I didn't really need the alibi to get in, and then after a while I just said, 'OK, enough, this is done.' "
As previously mentioned, Papillion will be released in theaters on Aug. 24.