The actor will play the role of a CIA interrogator -- whose sanity takes a perilous dive as he grapples with malevolent forces threatening the woman he loves. The movie doesn't have a major studio attached to produce or distribute ... for now, it's just an indie flick.

Despite his legal woes, JM's got some serious backup on this project -- it'll be directed by Martin Villeneuve, the younger brother of Oscar-nominated director Denis Villeneuve ... something sources connected to Jon have confirmed to TMZ.

Meanwhile, Christopher Tuffin -- the producer behind last year's quiet hit "Sound of Freedom" -- is spearheading the movie ... and he made clear he refuses to let public opinion affect who he casts ... saying he wouldn't be dissuaded from working with great artists.

Tuffin is expected to spill more deets on the Majors project during the Toronto International Film Festival in September -- but shooting is slated to begin in late Fall 2024 ... so we won't see what this looks like anytime soon. Unclear who else will star in the movie with JM.

"Merciless" appears to be the new movie Majors was spotted hitting the gym for recently -- remember ... we got pics of him working out back in March, and he later told us he was prepping for a possible role.

On its face, you could argue Jonathan is back in the swing of things post-assault trial -- where he was found guilty on 2 counts ... and acquitted of 2 others. He's still facing a lawsuit from Grace Jabbari in the aftermath of that ... but criminally, he won't do any jail time.

The guy got fired by Marvel -- which was his big break in the biz -- but now ... it appears he's inching his way back into the spotlight ... time will tell how well his efforts are received.