Eva Mendes is celebrating her 51st birthday in style — literally.The Hitch star, who shares daughters Esmerelda, 10, and Amada, 8, with long-term partner Ryan Gosling, posed in a dramatic Stella McCartney gown in an Instagram post shared on her birthday: Wednesday, March 5."My new campaign and my new age just dropped!" Mendes began the lengthy caption. "I'm 51 today and so grateful for all the reasons."Mendes went on to praise the iconic fashion designer "for making the most beautiful, cruelty free clothing that I feel so great in," gushing that she's "never felt sexier in anyone else's designs."Mendes' Instagram slideshow was made up of the same photo posted three times — one from McCartney's Summer 2025 campaign — all with varying degrees of close-ups. She wore a sheer black Stella McCartney dress that featured a nearly waist-high slit. The floor-length frock also featured a low neckline and a cutout at the hip. The Ruched Knotted Sheer Panel Maxi Dress retails for $3,600.While the actress shared her disappointment for not being able to attend McCartney's fashion show that day, she had the "best reason in the world" for missing it, she wrote."I'm with my family," she said.Mendes and Gosling, 44, met while starring in the 2012 film The Place Beyond the Pines. While it was life-changing for the couple, it was the Barbie star whose entire perspective changed after meeting Mendes."I wasn't thinking about kids before I met her, but after I met Eva, I realized that I just didn't want to have kids without her," he told GQ in 2023."And there were moments on The Place Beyond the Pines where we were pretending to be a family, and I didn't really want it to be pretend anymore," he added. "I realized that this would be a life I would be really lucky to have."