Juvenile -- Arrested for Hotel Fight

Rapper Juvenile was arrested for disorderly conduct at a Miami hotel last night after allegedly participating in a crazy brawl ... TMZ has learned.

Juvenile -- real name Terius Gray -- had just reunited with Lil Wayne on stage at LIV nightclub earlier in the evening ... when something went wrong.

Juve and Wayne -- who were in the Hot Boys together back in the late '90s -- had a long-running beef when the group broke up ... and last night was the first time they have been on stage together since the feud.

But around 7AM, cops say Juvenile -- who's listed at 5'11, 150 lbs -- was involved in a fight that began inside the nightclub and spilled outside to the front of the hotel.

Security told police the people involved in the fight were "creating a threat to life and property as well as the overall safety of the patrons inside."

Miami Beach PD responded to the scene and arrested Juve -- he was hauled to a nearby station where he was booked. He is still in custody.

8:30 AM PT -- Juvenile has been released from custody. He also told TMZ the fight was NOT with Lil' Wayne.