Charlotte Gainsbourg had better watch her back. Paris has a new It girl, Clémence Poésy. The 24-year-old favors a street-smart mix peppered with designer names like Balenciaga, Chloé, and Isabel Marant. Her perfectly unstudied style, coupled with a seriously enviable bone structure, have landed her in the front row at Chanel shows, on the cover of magazines (including the April 2007 i-D, cast by an admiring Nicolas Ghesquière), and now, in a coveted advertising campaign. Next spring, she'll appear alongside Chloë Sevigny and Anja Rubik as the faces of Chloé's newest fragrance. From whence did this budding fashion muse emerge? Poésy launched her acting career a decade ago in a play, Mai '45, Mai '95, written by her father, theater actor and director Étienne Guichard, but her international breakthrough came when she was cast as the haughty Fleur Delacour in 2005's Harry Potter and the Goblet of Fire. This month, she stars in two French films, Sans Moi and Le Dernier Gang. And we expect to see her in a front row or two again next season.