Nicole Kidman and Keith Urban Celebrate 18 Years of Marriage

Nicole Kidman and Keith Urban just celebrated 18 years of marriage -- and one stunning image captured their beautiful relationship.

The legendary actress posted an Instagram photo Tuesday, showing herself barefoot in a patterned dress lying back across a stone wall with a picturesque view of a foggy blue ocean. Her musician husband was sitting next to her while strumming an acoustic guitar.

In the caption, Nicole wrote, "Forever ❤️ #happyanniversary"

Unclear where exactly the couple jetted off to ... but they chose a wonderful spot for sure.

The romantic moment struck a chord with some of their famous friends. Naomi Watts stated in the comments section, "This looks like true love ❤️🙌❤️ heavenly 🙌❤️."

Rita Wilson also weighed in, saying, "Love you both. Happy Anniversary, lovers. ❤️."

In 2005, Nicole and Keith first crossed paths at the G'Day USA gala and were married in Australia one year later. They share two daughters, Sunday Rose and Faith Margaret.

Over the years, Keith has struggled with substance abuse issues and had to go to rehab, but Nicole helped him through the tough times.