Keith Urban honours his "gorgeous" wife Nicole Kidman on her 56th birthday.

On Tuesday the country singer, 55, shared a tribute to the Moulin Rouge actress on Instagram to celebrate her 56th birthday.

The One Too Many singer posted a photo of his wife from behind as she appeared to be watching an owl sitting on a tree branch.

“To my gorgeous, sexy, adventurous, curious, nature loving, owl spotting, artist, wife: happy birthday baby !!!!!! xxxxxx,” Keith gushed in the caption.

The long-time couple have been married since June 2006 and share two daughters, Sunday, 14, and Faith, 12.

Keith wasn’t the only person in the Big Little Lies actress's life to take to Instagram to wish her a happy birthday. Naomi Watts also shared a sweet tribute to her friend.

“Happy birthday my darling friend,” the King Kong actress wrote. “Here’s to more years of deep friendship and fun adventures. Love you to the moon. So grateful for your love and support.”

The two stars both acted in the 1991 drama/romance film Flirting. They have not worked on a film set together since then, however, they have remained good friends.