Lewis Hamilton Parties with Half Naked Supermodel!

Formula One champ Lewis Hamilton is having a GREAT day -- partying in Barbados with a half naked Chanel Iman ... who's stealing the show at one of the hottest festivals in the world!

The two are raging at the Crop Over festival -- where people strip down to their skivvies and party in the streets ... it's awesome!

Last year, Hamilton kicked it at the festival with Rihanna ... in between daggering sessions with some other hot ladies.

But this year, he teamed up with Chanel ... and check out the pics ... it's obvious why.