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The Australian actress sparkled in an Armani creation for the opening ceremony, opting for a strapless royal blue dress heavily embellished with gems, and a lace train.
The 46-year old actress swept her blonde locks into a chic side ponytail which showed off dangling Harry Winston earrings.
Alongside Nicole were her co-stars Tim Roth and Paz Vega, as well as French director Olivier Dahan.
Cannes is fitting for the film's premiere given that American starlet Grace, who Nicole portrays in the movie, met her future husband Prince Rainier at Cannes Film Festival back in 1955.
Also at the star-studded opening ceremony was this year's festival jury, headed by Jane Campion - the only female director to have ever won the festival's prestigious Palme d'Or.
Blake Lively at the premiere for Grace of Monaco
Fellow jurorsSofia Coppola, Carole Bouquet, Leila Hatrami, Do-Yeon Jeon, Willem Dafoe, Gael Garcia Bernal, Zhangke Jia, and Nicolas Winding Refn were also all in attendance for opening night.
Supermodel Karlie Kloss, Blake Lively, Zoe Saldana, Jane Fonda, and last year's Palme d'Or winning actress Adele Exarchopolous all also graced the red carpet with their glamour.