Reese Witherspoon and Naomi Watts helped pal Nicole Kidman ring in her 50s on Tuesday (20Jun17) by sending her birthday greetings on social media.

Reese wished her friend and Big Little Lies co-star a "gorgeous day" as the Australian actress hit the milestone age.

The 41-year-old wrote: "Wishing a big happy birthday to my dear friend, the one and only, #NicoleKidman!!! I hope you have a gorgeous day. Love you, lady!"

Meanwhile, Kidman's longtime mate Naomi also gushed about "this beautiful woman", adding, "A remarkable human who gives so much love and spirit to all those around her. 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..."

Both Reese and Naomi accompanied their greetings with recent photos of themselves with the birthday girl.