Opting for a pastel yellow gown, the 42-year-old Project Runway host showed off her glowing tan beneath the pale colour.
Her revealing gown, which featured a plunging neckline and thigh-high split, put her perfect model limbs on full display.
The stunning German added some glam to her sunny gown with some seriously impressive bling around her neck.
Heidi makes a statement
Showing off her cut-out back
We’re surprised the mum-of-four could keep standing upright with the elaborate drop necklace she was wearing.
Featuring a series of jewelled flowers, the piece finished with a sizeable blue rock, which hung into her cleavage.
She teamed it with a matching ring and jewelled earrings.
Alessandra gives it some leg
It seems thigh-high splits were the order of the evening at the glamorous event – with numerous models opting for the flesh-flashing style.
Joining the Victoria’s Secret model on the red carpet were the likes of Karlie Kloss, Alessandra Ambrosio and Jourdan Dunn.
All three models opted to show some leg – although they kept it monochrome in all-black gowns.
Karlie goes for frills
While Alessandra put on a very racy display in her low-cut ensemble, Karlie opted for a frilly off-the-shoulder number.
Meanwhile, 25-year-old Jourdan went asymmetric in a one-shouldered dress with exaggerated pleats.
So far the stars have turned out in force at the five-star Hotel du Cap-Eden-Roc to help support the global fight to end AIDS.
Jourdan Dunn at the amfAR’s 23rd Cinema Against AIDS Gala in Cannes
Katy Perry is set to perform at the event and models including Lara Stone and Barbara Palvin are expected to rock the runway for a charity fashion show.
Ahead of the fundraiser Heidi Klum wrote on Twitter: “Looking forward to joining @amfAR tonight! Proud to be supporting the fight to end #AIDS #amfARCannes.”