Mike "The Situation" Sorrentino's ex manager just filed a $1 million lawsuit against him ... alleging he was wrongfully dumped after taking him from "relative obscurity" to stardom.
The Manager's Co., Gotham NYC Entertainment, filed the suit today ... claiming the Situation dumped Gotham back in May for what he deemed a "lack of performance."
Gotham denies any poor performance -- but even if there was ... the lawsuit claims Sitch was contractually required to give Gotham 30 days notice ... and a chance to correct any issues.
Gotham claims it never got that opportunity -- and therefore Sorrentino is in breach of his contract.
In the suit, Gotham says it's managed Situation since the 2009 premiere of "Jersey Shore" -- and it not only discovered Sitch, but transformed "his career from relative obscurity to become an international celebrity."
Gotham is suing for damages in excess of $1 million.