Film producer Bradley Thomas -- who helped make "Killers of the Flower Moon" -- has suffered an unimaginable tragedy ... his wife took her own life this week, TMZ has learned.

Law enforcement sources tell us Isabelle Thomas jumped from a balcony at the Hotel Angeleno in the West L.A. area Monday night -- and we're told she was discovered dead at the scene when first responders arrived. Our sources tell us she leaped from a high-up floor.

Our law enforcement sources also say no suicide note was left behind.

Her death case is currently with the Medical Examiner's Office -- and they list it as a suicide. The official cause is attributed to multiple traumatic injuries ... consistent with a major fall.

Isabelle and Brad had been married since 2018, and they share two young children together -- and they were even pictured as recently as Jan. 13 at a public event.

It's a tragic turn of events for BT, no doubt, who's in the middle of Oscar season thanks to a movie he produced that's up for Best Picture -- namely, "Killers of the Flower Moon." He's produced tons of other movies over the years ... "Dumb and Dumber," "There's Something About Mary," "Kingpin," "Shallow Hal," "All the Money in the World," "Triangle of Sadness," etc.

Isabelle is survived by her husband and their two children. She was only 39.

RIP