More than 375,000 of the vehicles have been exported from the plant in Oxford, England, since its on sale date of July 2001.
The manufacturer had originally planned to build 100,000 MINIs a year but executives say that worldwide demand brought the half-million milestone two years early.
Dr Anton Heiss, managing director of BMW Group Plant Oxford, said: ‘We have reached this achievement through the commitment and flexibility of the 4,500 employees at the plant.
‘We are on schedule to produce more vehicles than the 174,000 MINIs built last year.’
More than 176,000 MINIs were sold in 2003 in 70 different markets. The 500,000th MINI is a dark silver MINI Cooper S bound for America.