Justin Timberlake attends Marine Corps ball as promised

Singer-turned-actor fulfilled his promise to escort a U.S. Marine who invited him via YouTube

Justin Timberlake promised Kelsey de Santis he’d be her date at the Marine Corps ball — and he proved to be a man of his word.

The sexy singer/actor was on the arm of the Marine corporal who asked him to be her date in a YouTube video in July.

Timberlake was snapped by a fellow partygoer looking dapper — and a little shellshocked — in formal wear at the Richmond, Va., event, seated at a table surrounded by Marines in uniform.

The wife of one of the Marines at the ball said Timberlake “posed for pictures and seemed like a normal guy,” according to WTVR.

De Santis, whose sassy YouTube invite was inspired by Timberlake’s encouragement of costar Mila Kunis to accept a Marine’s invite to a similar ball, talked tough before the event, telling reporters she planned to challenge Timberlake to a dance-off.

“My friends keep saying, ‘Dance-off!’ They know about my skills,” she told Access Hollywood.”

De Santis left the door open for things to heat up with the “Sexy Back” singer off the dance floor, in an interview before the event.

“Of course, I’m single!” she said. “I don’t know [if a kiss will happen. I guess that’s all up to JT and what his plans are.”

Kunis is still planning to attend the Marine Corps ball she was invited to, slated for Nov. 18.