Shirtless J.R. Smith made his return Thursday night ... and we all have Baker Mayfield to thank for it -- 'cause the Cavs star WENT CRAZY after the rookie led the Browns to a win!!!
It all went down at FirstEnergy Stadium in Cleveland ... where J.R. had luxury box seats to see the Baker-led Browns finally win a game for the first time since 2016.
You'll remember ... the last time J.R. celebrated a massive Cleveland victory -- he went topless in public for hours ... rockin' no shirt for the entire Cavs' championship parade.
Well ... about midway through the second half of the Browns-Jets game -- J.R. promised to make another shirtless appearance if they pulled out the comeback.
And then Baker did it -- AND OFF WENT THE SHIRT!!
"It's over! Let's go! Let's go!" a topless J.R. screamed after the win. "We outchya! No shirt shorty! We out here!"
Thanks again, Baker.