Jordin Sparks Is Dating Jason Derulo!

Perfect harmony!

Looks like Jordin Sparks has found her musical mate. The American Idol champ, 21, -- who dropped four dress sizes this summer -- happily snuggled with new beau Jason Derulo during a dinner date at Philippe Chow in West Hollywood on Sunday night.

The Ridin' Solo singer's rep confirms to Us Weekly that the pair have been seeing each other since August, when the pop stars played a show together in the Bahamas.

PHOTOS: American Idol stars' weight woes

An insider close to the new pair -- who were friendly for years -- explains that Derulo saw the slimmer Sparks "in a whole new light in the Bahamas. She lost over 30 pounds and looks amazing -- and he told her. It started there and they have been really reconnecting, now as lovers and not just friends."

VIDEO: Jordin surprises a fan with an at-home visit

Indeed, while celebrating Derulo's 22nd birthday on Sunday night the new lovebirds didn't try to hide their bliss.

PHOTOS: Hollywood's hottest bikini bodies

"Jordin would sing to him occasionally through the night in his ear if her head was rested on his shoulder," a witness tells Us. "It was Jason's only night in L.A. and the pair were excited to reunite."

Derulo's new album, Future History, hits stores Sept. 26. A rep for Sparks had no comment.