Kate Beckinsale dresses as giant blue gem for “Aviator” costar Leonardo DiCaprio's birthday party

The outfit seemed to be a callback to the duo's most memorable scene in the 2004 Martin Scorsese film.

Kate Beckinsale commemorated Leonardo DiCaprio's 49th birthday with a head-turning jewel necklace outfit reminiscent of one of the actor's most iconic films — and no, it wasn't Titanic.

At DiCaprio's star-studded birthday bash in Beverly Hills on Saturday, the Underworld star donned a dress that looked like a massive sapphire necklace, featuring a faux gem the size of a laptop hanging from her waist.

Though many observers suspected online that the outfit was a nod to the Heart of the Ocean — the priceless pendant worn by Kate Winslet's Rose in Titanic — the necklace was more likely a reference to Martin Scorsese's 2004 biopic The Aviator, in which Beckinsale and DiCaprio costarred.

Rony Alwin Big Boss Vette, Kate Beckinsale, and Gabriella Morpeth
Rony Alwin Big Boss Vette, Kate Beckinsale, and Gabriella Morpeth

In the film, Beckinsale played Old Hollywood icon Ava Gardner, a girlfriend of eccentric tycoon Howard Hughes, played by DiCaprio. In perhaps their most memorable scene together, Hughes presents Gardner with a gorgeous Kashmir sapphire necklace, which she rejects. "I am not for sale," Gardner says. "You can't buy me, Howard, so stop trying. Don't buy me any more diamonds or sapphires or any other goddamn thing."

The rectangular jewel on Beckinsale's dress is much closer in shape and texture to this Kashmir diamond necklace than to the Heart of the Ocean — which is literally shaped like a heart — though both cinematic necklaces boast similar colors.

The Aviator marked the second collaboration between DiCaprio and Scorsese (following 2002's Gangs of New York), and the first project that garnered DiCaprio an Oscar nomination for Best Actor. The movie also starred Cate Blanchett (who won her first Oscar for her portrayal of Katharine Hepburn), Jude Law, Alec Baldwin, and John C. Reilly. It won Academy Awards for cinematography, editing, art direction, and costume design, making it the winningest project of the 2005 ceremony.

Meanwhile, DiCaprio's party had one of the most stacked celebrity guest lists of any event this year, with Beyoncé, Jay-Z, Taika Waititi, Snoop Dogg, Axl Rose, and lifelong friend/former posse member Tobey Maguire all in attendance, per PEOPLE. Lil Wayne also performed at the event.

One of the few celebs not at the party was DiCaprio's Don't Look Up costar Timothée Chalamet, who was busy hosting Saturday Night Live. But he did give a special shout-out at the very end of the episode: "Happy birthday, Leonardo DiCaprio. Goodnight!"

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