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 sht,'” 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.

In another one of the resurfaced clips, Portnoy also made insensitive comments about Colin Kaepernick … saying the 49ers QB looked like an “ISIS guy,” and adding, “throw a head wrap on this guy and he’s a terrorist.”

The unearthed footage was immediately met with backlash … with critics calling for sponsors to drop partnerships with Barstool ASAP.

Initially, Portnoy defended the remarks … saying he was “uncancellable.” But after he says he spoke with his employees, the 43-year-old decided to issue a mea culpa.

“I can’t apologize for my existence, but I can be better,” Portnoy said. “And, I’m going to be better for [my employees].”

Portnoy says he’ll lean on the diversity of his staff to make sure situations don’t arise like this again in the future … adding, “To all the guys that work for me, I want you to know I have your back.”

“And, I want this to be a place that you fking can be proud of and if you’re not this second, we’ll get there. We’ll fking get there.”