For the "We Were" crooner's part, he posted a photo of the couple which features Urban with his arms wrapped around Kidman, 52.
"Thirteen years of magic , music, romance, wild adventures , and the ongoing discovery of pure love. Happy Anniversary Babygirl. xxxx - KU," he captioned the picture.
Meanwhile, the "Big Little Lies" actress posted a photo which shows Urban, 51, sweetly kissing Kidman on her forehead. "...love ❤️ Happy Anniversary Baby," she wrote alongside the snap.
The couple tied the knot in 2006. They share two kids together: daughters Sunday Rose, 10, and Faith Margaret, 8.
Earlier this year, Kidman shared a heartwarming story of the moment she knew that Urban was the one she wanted to marry and settle down with.
Speaking to People magazine at the time, the star talked about a time back in 2005 after she’d only recently met Urban at an event in Los Angeles. The duo grew closer in the following months before the country singer made a grand, romantic gesture to prove his affection.
“It was my [38th] birthday, and he stood outside with gardenias at 5 a.m. on my stoop in New York,” she told the outlet. “That is when I went, ‘This is the man I hope I get to marry.’”
Fox News' Tyler McCarthy contributed to this report.