The ergodic properties of rational billiards, i.e., billiards on a table whose angles are rational multiples of pi, have been a subject of intense study in dynamical systems. A famous result of Kerckhoff, Masur, and Smillie shows that rational billiards are uniquely ergodic in almost every direction. A famous result of Katok shows that rational billiards are not mixing in any direction. What about the intermediate regime of weak mixing, i.e., mixing modulo a negligible set of exceptions? In this talk we show that rational billiards are weak mixing in almost every direction unless a natural algebraic/geometric obstruction is present. Furthermore, this obstruction vanishes in 'most' cases. This is joint work in progress with Jon Chaika and Giovanni Forni.