Judge Who Sent Meek Mill Back to Prison Investigated by FBI

Meek Mill might have caught a huge break in his probation case and subsequent prison sentence fight -- 'cause the FBI is probing the judge who threw him back in jail ... TMZ has learned.

Law enforcement sources tell us Judge Genece Brinkley is being investigated by the FBI for possible relationships she might have in Philly -- including to a local music mogul, Charlie Mack, whom she asked Meek to sign with -- as well as a possible extortionate demand. The New York Post broke the story.

Undercover agents have reportedly been in the courtroom following Meek's case since April 2016, during which Mack allegedly once told Meek he knew the judge and could help him with his case. Mack has denied that claim.

As we reported ... Meek's lawyer says Judge Brinkley also once asked Meek to do a remix to a Boyz II Men song and to give her a shout-out on it, and that her harsh sentence was a result of him shooting her down.