What a year it's been for Serena Williams! She took home the coveted women's title at the US Open, won her 14th Grand Slam at Wimbledon, and picked up her third and fourth Olympic gold medals during the London Games. Today, the international tennis superstar celebrates her 31st birthday. In honor of the occasion, we're taking a look back at some of her most memorable tennis looks. Click through the gallery to see which of Serena's court styles made the cut.