Cara Delevingne shows off thong in completely see-through $10K gown

Cara Delevingne isn’t afraid to take a fashion risk.

She proved this to be true last night, baring it all in a completely see-through vintage gown on the red carpet for the world premiere of “Ocean With David Attenborough” in London.

The British model, 32, left little to the imagination, showing off her black lacy thong underneath the plunging mesh number, which happens to be made of fabric that’s around 100 years old.

Made in Cairo in the 1920s, the rare dress was created using tulle-bi-telli, a “hand-woven textile that originated in Upper Egypt during the 19th Century,” per Annie’s Ibiza, who sells the look for a whopping $10,040.

The striped neckline, meanwhile, was crafted from real silver. Delevingne covered up a bit, skipping a bra but layering a slouchy black boxy blazer over the fully sheer dress.

The model added more intrigue to the red carpet look with a black eagle pendant necklace and black peep-toe platform heels.

She posed on the red carpet with her older sister, Poppy Delevingne, 39, who is expecting her first child with her partner, Archie Keswick.

Poppy cradled her baby bump in a form-fitting black fringe gown, which she paired with a long black velvet coat.

The mother-to-be also wore the same eagle-shaped necklace in white.

The sisters’ animal-themed jewelry was perhaps a nod to the forthcoming National Geographic documentary.

“Ocean With David Attenborough,” which hits theaters on May 8, “shines a light on both the beauty of the sea and the ways in which humans are depleting its riches,” according to National Geographic.

Other celebrity guests last night included King Charles, Felicity Jones and Georgia May Jagger.