Leonardo DiCaprio has the best plan we've seen yet for saving our planet -- throw a huge party filled with smoking hot models and actresses ... and then kick back and watch the money pour in.

Leo's rich, gorgeous friends -- Michelle Rodriguez, Irina Shayk, Kate Hudson and Nina Dobrev --came out Wednesday night in St. Tropez for his foundation's annual auction, and helped him clean up. The event reportedly raised over $40 mil for his environmental charity, LDF.