"Happy Birthday to this beautiful woman," Watts, 48, wrote on Tuesday.
Naomi Watts, who’s been friends with Kidman for the better part of three decades, posted a sweet birthday message to her best friend on Instagram. “Happy Birthday to this beautiful woman,” the actress, 48, wrote on Tuesday.
“A remarkable human who gives so much love and spirit to all those around her,” Watts added. “My friend, I am so happy to have shared incredible experiences with you over the last 3 decades. May there be many more to come …”
The two became close starring together in 1991’s Flirting. “We already knew each other, but that’s when our friendship forged,” Watts recently told PEOPLE.
“We’ve gone through a lot together over a significant amount of time. That history binds you,” she continued. “We have a strong respect and love for one another.”
They also have children around the same age: Watts has two boys (Alexander, 9, and Samuel, 8) and Kidman has two daughters (Sunday, 8 and Faith, 6).
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Kidman’s Big Little Lies costar Reese Witherspoon also took to social media to celebrate her friend’s 50th. “Wishing a big happy birthday to my dear friend, the one and only, #NicoleKidman!!!” she wrote, adding, “I hope you have a gorgeous day. Love you, lady!”
Her other Big Little Lies costar Laura Dern also took to Instagram to commemorate Kidman’s special day, writing, “To the ever brilliant, bold, and beautiful, Nicole, happy birthday xx.”
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As for her birthday plans, Kidman told PEOPLE in February, “I always say, I get enough attention, so the last thing I need is a huge birthday party. I’m like, ‘low-key. Please, low-key!’ But definitely make me a cake.”
She added, “My favorite is coconut cake. I love coconut cake with 7-minute icing.”