Rapper Machine Gun Kelly -- Arrested for Disorderly Conduct

Rapper Machine Gun Kelly's tour took an unexpected stop early this morning -- to jail ... after he was busted by police in Florida for misdemeanor disorderly conduct.

According to the website for the Pinellas County Sheriff's Office, MGK (real name Richard Baker) was busted at 4:12 AM and released a few hours later after posting $100 bond.

Kelly tweeted about the arrest, saying, "Just spent my entire night in a f**king Florida jail...s**t escaladed way to quick last night, it always does with us though."