George Strait has been married to his wife ... To mark the major milestone, George serenaded his wife with his song "I Cross My Heart" during a concert in Las Vegas, per CMT.

Backstory: George Strait to receive Lifetime Achievement ... Some of Strait's biggest hits include "I Cross My Heart," "Ocean Front Property," "All My Ex’s Live in Texas," "Amarillo by Morning ...

The celebratory social media post was set to George Strait's "I Cross My Heart." "Five years ago they told us we needed to meet…God knew what He was doing. I thank Him for you, my best friend ...