Floyd Diaz, an undefeated boxer, was arrested in Sin City last week ... after Las Vegas Metro cops pulled the pugilist over while driving a stolen vehicle, TMZ Sports has learned.
During the stop, LVMPD also found the 21-year-old boxer was carrying a firearm he was not legally allowed to possess.
Diaz was initially stopped after a patrol unit received a LoJack alert indicating the vehicle was stolen.
The fighter was booked into the Clark County jail on two charges .