Catherine was appearing on the list for the second time, with her first mention in 2008 and has gained approval recently for her habit of recycling outfits including the green Diane Von Furstenberg dress she wore on her recent trip to California and again to William's cousin Zara's pre-wedding cocktail party.
Carla Bruni-Sarkozy, who is married to French president Nicolas Sarkozy topped the list with Sheikha Moza Bint Nasser of Qatar in second place and Catherine in third.
Michelle and Barack Obama also made their first appearance together on the Best Dressed Couples list. While Michelle has been among the best dressed ladies for the past four years, the president last appeared on the list back in 2009.
Colin Firth, Justin Timberlake and Formula 1 driver Jensen Button were among those included in the Best Dressed Men category.
International Best Dressed List:
H.H Sheikha Moza Bint Nasser of Qatar
H.R.H The Duchess of Cambrdge
H.S.H. Princess Charlene of Monaco
Jane Lauder Warsh