If there's any reason for the celebrity and style set to stick around the city come the last week of summer, it's the US Open. The beloved annual tennis tournament, which Anna Wintour never fails to make time for even when it stretches through New York Fashion Week, is buzzier than ever this year thanks to the GOAT, Serena Williams's announcement that she'll be retiring. Needless to say, the stars have stepped out to catch the very last of her professional matches. Click through to see this year's stylish A-list spectators over in Flushing.