The actress also took the opportunity on Wednesday to call out the people who criticized Gosling's casting as Ken prior to the premiere of the now highest-grossing movie of 2023 which received eight Oscar nods.
Alongside a screengrab of a publication that derided the actor titled in part "Ryan Gosling Is Giving Major Cringe as Ken in "Barbie," Mendes posted a note to celebrate Gosling's huge achievement on her Instagram post.
"So proud of my man," she wrote in the caption. "So much hate when he took on this role. So many people [were] trying to shame him for doing it."
She continued, "Despite all the #Notmyken ridicule and articles written about him, he created this completely original, hilarious,heartbreaking, now iconic character and took it all the way to Oscars."
"So beyond proud to be this Ken's Barbie 💕," she concluded the post.
Her post received tons of support online — including from Ryan's "Barbie" co-star, Supporting Actress Oscar nominee America Ferrera.
She praised his "triple somersault performance," adding, "I'm so grateful for the way he showed up with his super stardom, and continues to show up to support all the women in this process!! He is a class act and insanely deserving and talented."
Mendes excitedly responded to that reply in both English and Spanish, calling Ferrera a sister and congratulating the "queen" for her own nomination.
Mendes' Instagram post also came after Gosling made headlines on Tuesday after he spoke out about the 2024 Oscar nominations.
While expressing his gratitude for his nomination, the actor also shared his disappointment that "Barbie'"s director Greta Gerwig and star Margot Robbie were noticeably absent from two Oscar categories -- Best Director and Best Actress.
In a statement obtained by ABC News, Gosling said in part, "To say that I'm disappointed that they are not nominated in their respective categories would be an understatement."
"Against all odds with nothing but a couple of soulless, scantily clad, and thankfully crotchless dolls, they made us laugh, they broke our hearts, they pushed the culture and they made history," he added. "Their work should be recognized along with the other very deserving nominees."