John Davis -- the beloved host of "Coffee Time with John and Momma" -- is dead after suffering a medical episode during a livestream with his mother ... TMZ has learned.

Police in Jellico, Tennesee tell TMZ authorities were called to a residence just before 5:30 PM Wednesday ... and John was pronounced dead at the scene.

An official cause of death has not been released.

We've reached out to his family ... so far, no word back.

Funeral arrangements are being made at Harp Funeral Home, according to the venue's official social media page.

John and his mother had 200,000 followers on Facebook, where they'd livestream themselves cooking together, trying new recipes and sharing heartwarming stories about daily life.

We've seen the video of John's medical episode, but we're not sharing it here. It's still up on his YouTube page ... at least as of the time of this post.

John was 55.

RIP