Selena Gomez, Jared Leto, Bono, Marion Cotillard and Robin Thicke were among those who attended the auction event held in the Domaine Bertaud Belieu, a secluded hillside vineyard.
Other celebrities spotted arriving at the event – where invitations reportedly cost between $7,500 and $130,000 – included model Petra Nemcova, Cara Delevingne and Dynasty legend Joan Collins.
Proceeds from the evening benefit the actor's campaign to save Earth's wild regions and animals.
According to a statement released Thursday by his namesake foundation, DiCaprio, 39, kicked off the gala by telling the crowd, "There has never been, since the time of dinosaurs, as many plant and animal species disappearing so quickly … We must make efforts to protect rich biodiversity."
DiCaprio, who attended with girlfriend Toni Garrn, 22, then began the auction by selling a Harley-Davidson motorcycle autographed by Martin Scorsese and Robert De Niro.
Among other auction highlights:
Two "extras" roles in one of DiCaprio's upcoming films. Winning bid: a little over $3 million.
U2's Bono auctioned off his personal guitar for $1 million.
A Damien Hirst sculpture was picked up by U.S. billionaire Len Blavatnik for a little over $6 million.