The former O.C. starlet turns 25 today - happy birthday, girl!

And where is Mischa Barton celebrating her b-day? At a photo call for her film You and I (about two teenage girls who fall in love at a t.A.T.u concert) in Moscow. Party on!

Meanwhile, there's an online report circulating that Mischa is interested in joining Dancing With the Stars. Think that's a smart move for the actress?