She may have been at an event with fashion heavy-hitters Janet Jackson, Heidi Klum and Kylie Minogue, but "The OC" star Rachel Bilson stole the show in a gorgeous leopard print gown!

Rachel went to the 40th anniversary party for designer Roberto Cavalli in one of the designer's own creations -- which goes for $5,620 online.

FYI -- Bilson's dress has been modified, the original has two straps.