It's official! Britney Spears is engaged to marry Jason Trawick. According to sources at People, Trawick got down on one knee and popped the question to Spears last night (Dec. 15) on the eve of his 40th birthday.

"This is something they've both wanted for a long time," a source tells Us Weekly (via Rolling Stone). "It's a way to cement their family. They're both extremely happy and can't wait to become man and wife."

Another source tells People, "He surprised her after she gave him his gifts and after they had cake last night." The engagement ring is said to be Neil Lane sparkler.

Spears, 30, and Trawick will celebrate their engagement tonight in Las Vegas at Planet Hollywood."She's very happy. It's going to be a great weekend," the sources says.

Trawick is Spears' former manager, helping to run her career from 2008 up until early 2011. Britney's fiancee, who co-stars in her 'Criminal' video, retired from his position as her manager earlier this year in order to dedicate more time to their relationship.

Spears has two sons with her ex-husband, Kevin Federline. We hope that her kids -- Preston, 6, and Jayden, 5, -- are excited for their mom and soon-to-be step-dad!

Congratulations to Britney Spears and Jason Trawick! We wish you both all of the happiness in the world.