The star of The Northman, 55, took to Instagram to celebrate the joyful occasion with a rare throwback photo from the couple's wedding.

"Sweet XVI. Remember this like it was yesterday," Kidman captioned the photo, which featured the couple lighting candles together at their 2006 wedding ceremony in a church in Manly, Australia. Kidman wore a stunning one-shoulder wedding gown, with a long veil trailing behind her. A dapper Urban sported a black suit and tie as he smiled in the photo. "Forever."

Urban, 54, marked the milestone with a more recent shot of the longtime couple.

"HAPPY SWEET 16 BABY xxxxx," the country singer captioned a selfie that shows his Oscar-winning wife waving to the camera.

Urban's post comes just five days after he celebrated Kidman's 55th birthday with another sweet shot.

"Happy birthday babygirl," he captioned the photo, which features him planting a kiss on Kidman's forehead.

While the longtime couple have shared some of their joyful times on social media lately, they haven't been without any struggles during their relationship, which began when they first met at G'Day LA, a Hollywood event honoring Australians. Back in April, Urban spoke candidly with the Sunday Times about how influential the encouragement of his wife was in his lengthy battle with alcoholism. While he first checked into treatment in 1998, he returned to rehab a few months after marrying Kidman in 2006, at her insistence.

“My dad was an alcoholic, so I grew up in an alcoholic house and it took me a long time to believe I was wired the same,” Urban shared. “I had to find a different way to be in the world. I’m glad it didn’t change anything about my music. I wrote plenty of hit songs while drunk. I wrote plenty sober. I feel lucky it hasn’t defined my creativity.”

Back in the present, Urban recently gave his wife credit for helping him get back on track in the ballad, "Thank You," which he has stated was written in her honor.

The couple have two daughters together: Sunday Rose, 13, and Faith Margaret, 11. Kidman also has two children, Connor, 27, and Isabella, 29, from her first marriage to Tom Cruise, which ended in 2001