The custom made ensemble had a dramatic floral silk organza cape, which the 30-year-old Indian beauty paired with a pair of Ferragamo stilettos, and some bling on her fingers.
Sonam kept the make-up subtle by opting of pink eye-shadow and lips, while keeping her hair in a bun.
"@sonamakapoor wears a custom Ralph & Russo champagne silk crepe gown with embellished silk organza cocoon cape," the fashion house posted on Twitter.
Praising her attire, her father Anil Kapoor tweeted, "Sonam Kapoor's Breathtaking Attire at Day 5 of Cannes."
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This is Sonam's sixth year at the Cannes Film Festival. Her latest film "Neerja", a biopic on braveheart flight attendant Neerja Bhanot, will be screened in the market of the festival here.
She will also be a part of the prestigious amfAR gala on May 19.
Her Indian counterpart Aishwarya Rai Bachchan walked the red carpet on May 13 and 14. This year marked the former Miss World's 15th visit to the French Riviera.