On Tuesday, the singer shared a photo of himself and Kidman on the beach, with Urban's arms around his wife as the pair smiled amid a gust of wind.
"Thirteen years of magic , music, romance, wild adventures , and the ongoing discovery of pure love," he wrote. "Happy Anniversary Babygirl. xxxx - KU."
Urban and Kidman married in Manly, Australia in 2006, and Kidman shared footage from the special day on her and Urban's 12th wedding anniversary last year.
"Remembering 12 years ago today at a church in Manly, Australia," she captioned the video. "Still feels like it was yesterday. I’m a lucky woman. Happy Anniversary Baby."
Speaking to PEOPLE in January, Kidman revealed that the moment she knew she wanted to marry Urban was on her 38th birthday.
“It was my [38th] birthday, and he stood outside with gardenias at 5 a.m. on my stoop in New York,” the Oscar winner recalled. “That is when I went, ‘This is the man I hope I get to marry.'”
Urban then whisked Kidman off to Woodstock, New York, for a getaway on a motorbike.
“It was pretty intense,” Kidman said. “I believed by that point he was the love of my life. Maybe that’s because I am deeply romantic, or I’m an actress, or I have strong faith as well, but I just believed, ‘Oh, okay, here he is.'”
The loved-up couple never hesitates to share their feelings for one another, and Urban recently posted another tribute to his wife when he celebrated her birthday on Friday.
The CMA Entertainer of the Year filmed himself playing piano one-handed (the other hand was holding the camera), singing "Happy Birthday" to Kidman as he did his best to multitask.
After finishing the song with a flourish, Urban turns to the camera and says, "Happy Birthday, baby. I love you," blowing a kiss to cap off the video.
"Ok..... one handed ..... so I can film ....!" he wrote.
View this post on Instagram
Photo Credit: Getty / Jeff Kravitz/ACMA2019