November 4, 2022 | 7:34pm

On Thursday night, music legend Joni Mitchell, who turns 79 next week, attended the opening performance of Cameron Crowe’s “Almost Famous,” and it turns out it was her very first time seeing a show on Broadway.

A spy overheard Mitchell telling her audience mate, Clive Davis, “that she had never seen a show on Broadway before this,” they told Page Six.

Mitchell revealed the detail to Davis during the show’s intermission, but we hear she “made a dramatic entrance” right before the start of the show.

“She gamely smiled for photographers and took a huge ovation in stride,” the source said.

Mitchell was seated next to Clive Davis and was overheard telling him it was her first time on Broadway.

Bruce Glikas/Getty Images

Mitchell was seated next to Clive Davis and was overheard telling him it was her first time on Broadway.

Bruce Glikas/Getty Images

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But it wasn’t Mitchell’s first time seeing the show.

She sang the show’s praises to Broadway legend Tommy Tune, explaining that she actually attended the opening of the musical’s premiere in San Diegoand loved it then.

Mitchell met with the cast for a champagne toast after the performance.

Bruce Glikas/Getty Images

Mitchell joined the cast for a champagne toast after the performance.

Bruce Glikas/Getty Images

Mitchell joined the cast for a champagne toast after the performance.

Variety via Getty Images

Mitchell joined the cast for a champagne toast after the performance.

Variety via Getty Images

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Our source overheard Mitchell describing the show as “better now, and better than the movie!”

We’re told the cast was eager to meet Mitchell after Thursday night’s performance.

They waited on stage to greet her and take photos, followed by a champagne toast we’re told. Jann Wenner, Paul Rudd, Joe Scarborough and Mika Brzezinski were some of the other notables who took in opening night.

Pennie Trumbull, who inspired the character Penny Lane, was also in the audience.

The cast celebrated with an afterparty at Starchild Rooftop at the Civilian Hotel.

Crowe told The Post of the film’s success, “It actually got demolished by a re-release of ‘The Exorcist,’ a movie from 1973″ when it opened. He added, “There was also aJamie Foxx moviethat came out that weekend that did really well. But what happened was VHS. The VHS tape of ‘Almost Famous’ gathered steam for us. And so that’s, you know, probably accurate too, it’s like the ’70s-ish thing. So, like, the antique version of film watching is what gave us success.”