Fox News apologized on Monday after a guest on the network attacked 16-year-old climate activist Greta Thunberg as a “mentally ill Swedish child.”

The comments by Michael Knowles of the Daily Wire, who appeared on “The Story,” came hours after Thunberg delivered an emotional speech at the United Nations berating world leaders for failing to act on climate change.

But Knowles didn’t see an impassioned young activist fighting for her planet.

Instead, he repeatedly called Thunberg “mentally ill” and claimed she was “being exploited by her parents and by the international left.”

Democratic commentator Chris Hahn, also on the show, immediately called him out for it.

“You’re a grown man and you’re attacking a child,” he said. “Shame on you.”

Knowles replied: “I’m not. I’m attacking the left for exploiting a mentally ill child.”

But Hahn didn’t let it slide.

“Relax, skinny boy, I got this, OK? You’re attacking a child,” he said. “You’re a grown man. Have some couth.”