Paul Preece Jr. -- the winner of the first season of Netflix's nature survival competition show "Outlast" -- is facing serious criminal charges in Tennessee, including alleged rape of a child ... TMZ has confirmed.

According to jail records, seen by TMZ, Preece was arrested in Knox County on March 6 and charged with rape of a child, aggravated sexual battery and attempted rape of a child.

The case stems from a capias warrant, though further details about the allegations have not yet been publicly released.

On "Outlast," contestants form teams and compete to survive in the Alaskan wilderness for a $1 million prize. During the show's first season in 2023, Preece split the winnings with fellow Charlie Camp members Seth Lueker and Nick Radner.

We reached out to Preece ... so far, no word back.