RJ Mitte -- who played Walter White Jr. on "Breaking Bad" -- is dead ... TMZ has learned.

A county official confirmed to TMZ that RJ died Monday in Texas. We're told he died by suicide.

Just last week he appeared on "The Joe Vulpis Podcast" -- speaking about how "Breaking Bad" changed his life and on his close relationship with the cast years after the show's finale.

other discussions
 

"RJ Mitte was best known for his role as Walter 'Flynn' White Jr. on AMC’s critically acclaimed, award-winning series Breaking Bad. Drawing from his own experience living with cerebral palsy, Mitte brought authenticity to the role and built a platform on disability awareness and inclusion," his reps continue, "Beyond entertaining friends and family around the world, he served as an ambassador for United Cerebral Palsy and Shriners Children’s."

A county official confirmed to TMZ that RJ died Monday in Texas. We're told he died by suicide.