Léa Hélène Seydoux-Fornier de Clausonne (French: [lea sɛdu]; born 1 July 1985) is a French actress. Prolific in both French cinema and Hollywood, she has received five César Award nominations, two Lumières Awards, a Palme d'Or and a BAFTA Award nomination. In 2009, she won the Trophée Chopard Award for Female Revelation of the Year at the Cannes Film Festival. In 2016, Seydoux was appointed a Dame of the Order of Arts and Letters. In 2022, the French government made her a Dame of the National Order of Merit.

She began her acting career with her film debut in Girlfriends (2006), with early roles in The Last Mistress (2007) and On War (2008). She won acclaim for her French roles in The Beautiful Person (2008), Belle Épine (2010), and Farewell, My Queen (2012). During this time, she expanded her career by appearing in supporting roles in high-profile Hollywood films, including Quentin Tarantino's Inglourious Basterds (2009), Ridley Scott's Robin Hood (2010), Woody Allen's Midnight in Paris (2011) and the action film Mission: Impossible – Ghost Protocol (2011).