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.