Jeff Bezos and Lauren Sánchez’s closing night pajama-themed party in Venice, Italy, raged ’til the wee hours, with a source telling us it was a “dance party” with famous guests busting moves to Usher and DJ Cassidy.

A source tells us, “Oprah [Winfrey] and Gayle [King] were tearing up the dance floor.”

We hear Rolling Stones frontman Mick Jagger was also showing off his famous moves.

Other “big dancers of the night” ruling the floor were Kris Jenner and boyfriend Corey Gamble, Tommy Hilfiger and wife Dee Ocleppo and Jerry Seinfeld’s wife, Jessica Seinfeld.

And actress Sydney Sweeney “was dancing all night.”

The newlyweds were also cutting a rug, we hear.

A spy tells us that Usher, a personal friend of the power couple, performed a medley of his greatest hits and even got into the crowd.

“Usher came off stage and was in the middle of everyone,” says the source.

Superstar DJ Cassidy, who also played Jay-Z and Beyonce’s 2008 wedding, opened the night in one room, performing with a full orchestra.

He later played again following Usher’s performance, with the party raging until 3 a.m.

“It went late,” says the source, who called it “an all-nighter.”

Bezos, 61, and Sánchez, 55, also got on stage.

“The bride and groom went on stage with Cassidy and were dancing,” says the spy.

Guests — including new bro pals Tom Brady and Orlando Bloom, Leonardo DiCaprio and girlfriend Vittoria Ceretti, Kim Kardashian, Jessica Alba, Bill Gates, Brooks Nader, Ivanka Trump and designer Stacey Bendet — were treated to a buffet-style meal of Italian treats like pastas and desserts like cannoli, says the spy.

Guests wore their finest silks, slippers and pajama-inspired looks, with the spy telling us that “the men were much more on theme.”

We’re told the decor at the wedding, located in the Arsenale area of the floating city, was Venetian luxe.

“There were big red velvet banquets and couches, and plush pillows,” says the spy.

The location, which was changed at the last minute to avoid protesters and crashers, was on the water in a position that made it impossible to access.

“I didn’t see any paparazzi or press,” says the source, noting that they had been circling on boats or standing in nearby canals at other events.

The final night dance party was the culmination of three days of festivities for Bezos and Sánchez.

The Amazon billionaire and the former journalist said “I do” on Friday during a ceremony on San Giorgio Maggiore island that included performances by Andrea Bocelli’s son Matteo Bocelli and pop star Ellie Goulding.

During the first night, guests, who also include Diane von Furstenberg and Barry Diller, gathered for an event at Madonna dell’Orto.