IT’s thrills and chills backstage at TV’s “American Horror Story: Coven” – with the show turning into a clash of dueling divas!

Insiders say Jessica Lange, 64, announced she’ll leave the creep-tastic FX series after next season because producers want to hire more veteran actresses, including 80-year-old Joan Collins.

Emmy winner Jessica, who plays a witch seeking the fountain of youth, was thrilled when her pal Kathy Bates, 65, of “Misery” fame signed on for the show’s third season, sources say.

But then the acclaimed actress  Angela Bassett, 55, joined the cast.

“Jessica ruled the roost on ‘Horror Story’ for the first two seasons, but now she’s got a lot of competition,” said a source.

“Kathy’s been chewing up the scenery, and Angela’s also been given a major story line. All three are angling for more screen time.”

Now creator Ryan Murphy is said to be putting out feelers to “Dynasty” star Collins. “Ryan loves the idea of adding older divas to the cast and reigniting their careers,” said a source.

Oscar winner Sissy Spacek, 63, star of the original “Carrie,” and “Knots Landing” beauty Donna Mills, 72, are also apparently on his wish list for the show, which changes settings, story lines and characters each season. And it’s on a roll as this season’s premiere was watched by nearly 6 million people.

“Jessica loves Kathy,” said the source. “But adding Angela with plans to hire even more veteran actresses makes her feel as if she’s being pushed out of a job.”

Another insider added: “As far as Jessica is concerned, the show ain’t big enough for all of them!”