Britney Spears is set to marry for a third time, following her engagement to boyfriend Jason Trawick.

The singer tweeted her excitement last night: "OMG. Last night Jason surprised me with the one gift i've been waiting for. Can't wait to show you! SO SO SO excited!! Xxo"

It seems the night was a double celebration as Spears threw a birthday party for her fiancé which was held in Las Vegas to celebrate Trawick's 40th birthday.

The singer and her fiancé began dating in 2009 and the pair met while Trawick was acting as Spears' agent, a role he left in May of this year.

She followed her excited tweet with another: "Still glowing! About to jump on a plane to Planet Hollywood in Vegas. Throwing a Bday Party for Jason at Chateau Night Club. So fun. Xxoo"

The engagement ring is a three carat Neil Lane diamond ring.

This will be Spears' third marriage: She famously wed childhood friend Jason Alexander in Vegas and the marriage lasted a mere 55 hours.

Her second marriage, to back-up dancer Kevin Federline, father of her boys Sean Preston and Jayden James, ended with Spears filing for divorce in November 2006.