Kim Kardashian is sending a special birthday message across the pond to Duchess of Cambridge Kate Middleton ... who turns the big 3-0 today!

However, the 31-year-old reality star, wearing a low cut animal print blouse, didn't waste an opportunity to plug one of the products she represents in the process.

After the brief b-day message, Ms. Kardashian just so happened to mention a special ShoeDazzle offer involving a new heel called "The Duchess."

Such a business savvy kind person!