Barstool Sports honcho Dave Portnoy is apologizing for his past on-camera usage of the N-word ... and he's now vowing to do better going forward.
"I should have had [my employees'] back from the beginning and been like, 'Yup, I wish I didn't f**king say that sh*t,'" Portnoy said in a video Thursday. "I'm sorry I said it. I'm sorry it offended people."
"I was just trying to be f**king funny."
Clips from around four years ago surfaced of Portnoy this past week ... showing the Barstool Sports founder saying and rapping the N-word on company-produced content videos.