Jon Gosselin fiercely defended his son Collin after the 22-year-old’s new memoir made shocking allegations against his mother, Kate Gosselin.

Jon said he was proud of Collin’s bombshell book, “In the Shadow of Eight: Surviving the Reality of My Childhood,” and shut down any allegation that he’s mentally ill — which Kate claimed in a TikTok comment Tuesday.

“First and foremost, I couldn’t be more proud of my son’s heartbreaking memoir and his mission to help other victims of abuse,” Jon told Us Weekly in a statement Thursday.

“Also, let me be very clear: If you continue to falsely label my son Collin as ‘mentally ill,’ you will be held accountable,” he continued. “As you know, Collin has been evaluated by multiple independent psychiatrists, and that narrative is proven categorically untrue.”

The former reality star, 49, noted that repeating false claims about Collin’s mental health is “damaging to his reputation, his credibility and his future.”

He concluded, “Consider this fair warning: The days of using mental health to discredit and silence my son are over.”

In Collin’s memoir, released Tuesday, he describes his mom’s alleged wrongdoings throughout his childhood and her decision to put him in a mental institution in 2016. Collin claims Kate only visited him once and brutally told him, “You broke our family.”

Among the shocking allegations was that she kept him locked up in “a small holding” cell for two years before sending him away to the mental institution when he was 12 years old, isolating him from the rest of his siblings.

He also claims his now-estranged mom forced her eight children — fellow sextuplets Alexis, Aaden, Leah, Joel and Hannah, as well as twins Cara and Madelyn (now 25) — to act a certain way in front of cameras while the family filmed their hit TLC show, “Jon and Kate Plus 8.”

Kate, he claims, had unreasonable expectations of them as young toddlers, and would then dole out brutal punishments as consequences.

He writes, “If we got even the littlest bit of dirt on our clothes, we’d be stripped down and punished.”

Kate, 51, hit back via TikTok after the book’s release, when she responded to to a supporter who labeled Collin’s claims as “terrible lies” and said it “should be illegal to defame someone” in a memoir.

Kate commented, “Rational logical [people] or anyone who has dealt with mental illness understands what’s going on here.”

Kate also “liked” a comment that alleged Collin would “regret all of this someday” and that he was “encouraged and enabled by other dysfunctional and mentally ill people.”

Collin exclusively told Page Six Tuesday that he’s weighing his legal actions against his mom concerning the alleged abuse that he suffered, including filing a potential police report.

“I have the grounds to do so,” Collin told us. “And this justice is very important to me for all children to know that they should absolutely fight and they should actually look into what has been done to them and never stop fighting it.”