Prince Harry branded Prince William his “arch-nemesis” in his hotly-anticipated bombshell memoir, “Spare.”

The Duke of Sussex’s harsh words were quoted by Good Morning America anchor Michael Strahan in a teaser for his one-on-one interview with Harry.

“There’s a quote in the book where you refer to your brother as your ‘beloved brother and arch-nemesis,'” Strahan tells the duke. “Strong words. What did you mean by that?”

“There has always been this competition between us, weirdly,” Harry responds. “I think it really plays into — or is played by — the ‘heir, spare.'”

The full interview is set to air Monday morning.

The revelation comes just hours after the Guardian published an excerpt from the memoir, in which Harry alleges that he was left battered and bruised when the Prince of Wales tossed him to the floor in a bitter fight two months before he and Meghan Markle left the royal family.

According to Harry, William wanted to speak with his brother about “the whole rolling catastrophe” of their relationship and struggles with the press, which he pointedly blamed on his brother’s wife Markle.

William reportedly called the former “Suits” actress “difficult,” “rude” and “abrasive,” before Harry fired back that he was only parroting the negative “press narrative” the couple has extensively spoken out against in recent years.

The brothers continued shouting at one another until Harry accused his older brother of acting like an heir and not understanding why his younger sibling was not content with being a spare, Harry said.

The release of Harry’s memoir on January 10 is accompanied by two sit-down interviews — the aforementioned Strahan interview, and with ITV’s Tom Bradby in the UK, respectively.

In the second trailer of his conversation with Bradby, Harry refused to commit to attending his father King Charles’ coronation in May.

When asked whether he’d attend the event if invited, the Duke of Sussex said “there’s a lot to be discussed” before he can make that decision.

“There’s a lot that can happen between now and then,” Harry said. “But, the door is always open. The ball is in their court.”

“There’s a lot to be discussed and I really hope that they’re willing to sit down and talk about it,” he added.

When asked about his brother’s reaction to his constant — and high-profile — bashing of the firm since quitting royal duties in 2020, Harry responded, “He’d probably say all sorts of different things.”

The clip was shared hours after Page Six reported exclusively that William and his now-wife Kate Middleton told Harry to don a Nazi uniform for a 2005 costume party.

Harry also accused his dad of immediately branding him a “spare” on the day he was born — and joking that his “work” was done with then-wife Princess Diana.