The Leonardo DiCaprio Foundation's annual fundraising gala on Wednesday night in St. Tropez. France, was definitely the place to be.
Besides featuring an epic Titanic reunion, Madonna also surprised guests with a performance. The 58-year-old singer Instagrammed a video of her singing "4 Minutes," rocking a feathery suit.
"Such an honor to be here supporting Leo's foundation and doing what we can to save Planet Earth!" she wrote.
WATCH: Kate Winslet and Leonardo DiCaprio Reunite With 'Titanic' Co-Star Billy Zane -- 'Now We're Saving Icebergs'
"Tonight in St. Tropez was fire!!" she added.
Later, the Material Girl shared a picture with the man of the hour himself.
"This Man is a BOSS!!" she gushed. "Thank you Leo for all you do for Mother Earth! Your generosity and care is beyond measure!"
Other A-lists guests at the gala included Madonna's ex, Sean Penn, as well as Jared Leto, Cate Blanchett, Kate Hudson, Tom Hanks, Marion Cotillard, Uma Thurman and Edward Norton.
Proceeds from the event go to DiCaprio's foundation, which offers grants to environmental causes. The foundation is also holding an auction -- raising $30 million so far -- with incredible prizes, including a dinner with both DiCaprio and his longtime pal, Kate Winslet.
WATCH: Leonardo DiCaprio and Kate Winslet Will Reunite to Auction Off a Dinner With Themselves for Charity
ET spoke with Winslet earlier last month at the junket for her upcoming movie, The Mountains Between Us, where she revealed the lessons she learned from Titanic.