President Obama led a conga line, took part in a “Gangnam Style” dance-off with Usher, and even did the electric slide at his celebrity-packed inauguration bash at the White House.

Barack and Michelle danced past 3 a.m. at the spectacular private bash in the East Room for their closest friends and supporters.

One guest told us, “The president and Usher had a dance-off to ‘Gangnam Style’ along with Janelle Monáe. The president was a good dancer, but Usher threw down some amazing Michael Jackson-style moves.

“They played ‘Single Ladies.’ and all the women were dancing, led by Michelle. Later, everyone lined up and did the electric slide, and the president led a party line around the room. Most people did the conga with him. The only people who weren’t dancing were Bill Clinton (without Hillary), Timothy Geithner and John Kerry.

“Pick any party you’ve ever been to, this was a thousand times better,” our source said.

Even though Obama has embraced social media better than any other politician, the invite to the super-exclusive bash — which took place after the formal inaugural balls — strongly stipulated “no social media.”

Guests were treated to cocktails and food in the Lincoln Room before the party got under way with performances by Eric Benét and Monáe. Later, DJ Cassidy spun party tunes, and stars including Katy Perry — with John Mayer — Usher, Swizz Beatz, Jennifer Hudson and Alicia Keys did impromptu performances. Cassidy played “Empire State of Mind,” and Keys sang her part live over the mike.

Other guests included Colin Powell, Susan Rice, Eva Longoria, Gayle King, Ashley Judd, Al Sharpton and Rahm Emanuel. The business world was represented by power players including American Express CEO Ken Chenault, 32 Advisors’ Robert Wolf and Honeywell’s David Cote. Missing were Anna Wintour, who was at the Paris couture shows, David Geffen and Oprah Winfrey, who we’re told had a speaking engagement in Canada.