July 15, 2021 | 10:36am

Jason Tartick is firing back at trolls who attacked his fiancée Kaitlyn Bristowe’s appearance.

“I don’t know why people think it’s OK to say the s–t they do on Twitter,” the former “Bachelorette” contestant, 32, said on his “Click Bait with Bachelor Nation” podcast Thursday.

“There’s so many things in this world we can control, and there’s so many things we can’t control. Our looks and things like that are most of the things we can’t control,” he continued. “And the way that people make comments, nasty comments, about people’s appearances — and obviously, specifically, I’m referring to Kaitlyn — it’s grotesque. It’s a joke.”

Since Bristowe, 36, began co-hosting Katie Thurston’s season of “The Bachelorette” following Chris Harrison’s exit, she has been on the receiving end of numerous negative comments online about how she looks different now than she did when she was the the Season 11 “Bachelorette” in 2015.

“I don’t see why people have to do that,” Tartick said. “And the other thing is, the fact that it’s usually women putting other women down is just insane. When Chris Harrison was up there, were people talking about Chris Harrison’s looks? Or when a guy’s up there?”

Bristowe herself was recently forced to stick up for herself, tweeting in June that she was “so sick of women commenting” on her face.

She also hit back at someone who called her look “different,” writing, “6 years since I was on the show, Brow lift, brow micro blading, got my teeth bonded, some filler In my lips, aging, darker hair, and I finally learned how to contour. Oh and I put on some weight.”

In a Twitter video, Bristowe added, “Let me clarify brow lift because I’m having a chuckle over here, clearly by myself. … I didn’t go under the knife. All my friends are like, ‘What?’ No, I just got Botox to lift the brows.”

The “Bachelor” alum joined the franchise in 2015 when she competed for Chris Soules’ heart. She co-led “The Bachelorette” with Britt Nilsson later that year, when Bristowe met and got engaged to Shawn Booth. They split in 2018.

Bristowe quickly moved on with Tartick, who proposed to her in May after she finally won a competition — “Dancing with the Stars.”