When you're about to get one of the richest contracts in sports history ... what do you get your wife for her birthday?
Bryce Harper got his wife THE BACKSTREET BOYS!!
The MLB superstar took his wife to see the guys at Planet Hollywood in Vegas over the weekend -- and not only got her backstage for a meet and greet ... but, had the guys take her on stage for a 5-on-1 serenade!
Check out the video as Kayla Harper gets a flower and a special rendition of "Shape of My Heart" from AJ, Howie, Nick, Kevin and Brian!
After the show, Kayla wrote, "My 9 year old self lost her mind last night. Bryce has been surprising me with little gifts all week and one of them happened to be a black dress that he said I needed for Sat night."
"He let me know at dinner that he was taking me to see the Backstreet Boys... little did I know, the biggest surprise of them all was meeting them & then having them pull me onstage to be serenaded."
So, how much did it cost? Doesn't matter to Bryce -- who's expected to sign a contract that could be worth hundreds of millions of dollars!