The actor has been added to the cast of the Amazon show for season three, in which he will play World War II veteran Soldier Boy, a character described as "the original superhero," who became "the first super celebrity, and a mainstay of American culture for decades."
The role will reunite Ackles with "Supernatural" creator Eric Kripke, who adapted "The Boys" from the comic book of the same name, and serves as showrunner and executive producer.
Joking about Ackles' casting in a statement, Kripke quips, "When I was a child, I had a crazy, impossible dream - to provide Jensen Ackles with gainful employment. I'm happy to say that dream has come true."
"Jensen is an amazing actor, an even better person, smells like warm chocolate chip cookies, and I consider him a brother."
"As Soldier Boy, the very first Superhero, he'll bring so much humor, pathos, and danger to the role. I can't wait to be on set with him again, and bring a bit of 'Supernatural' to 'The Boys'."
Ackles is currently preparing to film the last few episodes of "Supernatural" 15th and final season, which were delayed due to the COVID-19 pandemic.
A production date for season three of "The Boys", which stars Karl Urban, Jack Quaid and Chace Crawford, has yet to be revealed, but the casting news emerges ahead of the second season premiere on 4 September.