Lindsay Lohan has had her probation revoked by a Los Angeles judge and will now learn when -- not "if" -- she'll be reporting to prison.

Commissioner Jane Godfrey apparently got fed up with Lindsay's constant flaunting of the law and dropped the bombshell this morning at a hearing -- which Lohan did not attend. The hearing was initially to be an arraignment on reckless driving charges from her Porsche wreck last year, but was expanded to include her jewelry theft case -- the one she was already on probation for.

With the probation revoked, LiLo must appear in court on January 15th to find out how much jail time she'll serve -- the max being 245 days.