There was Gatsby.

At 11:30 p.m. on Thursday night in the South of France, the amfAR Cannes gala quietly welcomed one of the biggest movie stars in the world to dinner in a tent off the Mediterranean Sea. Leonardo DiCaprio had been missing for several years at the glitzy charity auction that marks the end of partying at the Cannes Film Festival, but this year, he brought a date — his mom, Irmelin Indenbirken.

Leo, who came to Cannes with Martin Scorsese’s “Killers of the Flower Moon,” took the back entrance into the party, skipping the red carpet packed with European influencers and socialites taking selfies in ballgowns that looked like prom dresses. At Table 15, near the stage at the Hotel du Cap-Eden-Roc, DiCaprio tried to go incognito (as if that was possible). He wore a baseball cap to the black-tie dinner and kept his head down. He watched with amusement as celebrities tried to wrangle hundreds of thousands of dollars from oligarchs and mysterious moguls for lavish pieces of arts, vacations and even a car.

DiCaprio’s pal Tobey Maguire — dressed in a mishmash of a black suit, gold chain and sneakers with brown soles — kept pacing around the tent. Didn’t he have a seat?

But back to Table 15. Throughout the night, DiCaprio whispered to his mom and applauded for the musical acts (including the night’s headliner Halsey). But he disappeared during one of the biggest moments of the dinner, in yet another effort not to draw any attention to himself.

At around midnight, the charity devoted to raising money for AIDS research unveiled a one-of-a-kind portrait of DiCaprio. Two men rolled the large canvas of art onstage, as if they were handling the Mona Lisa. This was not a gag — it was, in fact, actually valuable. According to the auctioneer, Damien Hirst had been commissioned to paint the “Titanic” star. Then, some time later, the painting was sold to a private collector, who had donated it back to amfAR to give someone else the opportunity to hang Leo in their living room. As the bids flew, DiCaprio’s mom stood up with her phone to film all the rich people fighting over a portrait of her son. She looked ecstatic as the final bid was called. Sold! For $1.3 million.

amfAR Cannes used to draw star power from the world’s most glamorous film festival in the South of France. But in recent years, the tent has struggled to fill A-list names, as amfAR battled a series of scandals. In 2018, its chairman Kenneth Cole resigned after multiple investigations detailed how Harvey Weinstein used the nonprofit for shady dealings. In her memoir, “The Beauty of Living Twice,” Sharon Stone wrote about how disappointed she was to question what happened to the money that she raised at amfAR Cannes.

But if there were any such doubts that lingered, they disappeared with every uncorked bottle of champagne. Queen Latifah emceed this year’s 29th annual gathering, delivering scripted remarks. “With your help everybody, this evening we can and will end the HIV/AIDS epidemic,” she said to a smattering of applause. Famed charity auctioneer Simon de Pury then took over, pounding his gavel as thousands of guests spoke over him, wondering why the dinner was being served so late. Beyond DiCaprio, the talent in attendance ranged from Alex Pettyfer to Heidi Klum. “No one good is here!” grumbled one guest.

Eva Longoria and James Marsden proved to be two of the more successful presenters, as they helped pump up the bidding for a new Aston Martin sportscar that fetched $1.6 million. Other items that sold for hefty price tags: a pair of white-gold earrings from Chopard ($300,000); a collection of 18 gowns from fashion’s biggest designers — Versace, Prada, Chanel, Balmain, Dior, Givenchy, Louis Vuitton and more — presented in a runway show (a mere $650,000 for a whole new closet); and a stainless steel glass sculpture by artist Anthony James that had been featured in “Glass Onion: A Knives Out Mystery” ($270,000).

The evening began with a performance from Gladys Knight belting out “Midnight Train to Georgia,” flanked by a trio of backup singers (yes, she hit all the high notes). Adam Lambert, who donned a sparkling black tuxedo, dedicated the Queen song “Who Wants to Live Forever” to the memory of Tina Turner. Beba Rexha shimmied in a sparkling blue pantsuit as she crooned her banger “I’m Good (Blue).” The night ended with Halsey, cranking through a four-song set list that included her signature hit “Without Me.”

Then, the crowd scurried down a hill to the hotel’s restaurant for the after-party. But a shortage of food led guests to try to break into the kitchen as a manager pushed them back — saying the French Fries were for room service orders only.

Leo and Tobey held court in the VIP area outside by the pool. At 1:30 a.m., DiCaprio left with a 10-person entourage, including his mom. He gently patted her shoulder on their way out — winning the prize at Cannes of “best movie star son.”