Léa Hélène Seydoux-Fornier de Clausonne (born July 1, 1985) is a French actor. She began her acting career in French cinema, appearing in films such as The Last Mistress (2007) and On War (2008). Seydoux first came to attention after she won the Trophée Chopard and received her first César Award nomination, for her performance in The Beautiful Person (2008).

In the years that followed, Seydoux began appearing in minor 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). In French cinema during this period, she was nominated for the César Award for Most Promising Actress for a second time for her role in Belle Épine (2010) and was nominated for the César Award for Best Actress for her role as a lady-in-waiting to Marie Antoinette in the film Farewell, My Queen (2012).

Seydoux came to widespread attention in 2013 when she was awarded the Palme d'Or at the Cannes Film Festival for her role as a lesbian art student in the critically acclaimed film Blue Is the Warmest Colour, along with its film director Abdellatif Kechiche and her co-star Adèle Exarchopoulos. That same year, she also received the Lumières Award for Best Actress for the film Grand Central and, in 2014, she was nominated for the BAFTA Rising Star Award and starred in the films Beauty and the Beast, Wes Anderson's The Grand Budapest Hotel and Saint Laurent. She gained further international attention for her appearance as Bond girl Madeleine Swann in Spectre (2015), a role which she reprised in No Time to Die (2021). Since then, she has continued to appear in major English-speaking roles in The Lobster (2015), in Wes Anderson's The French Dispatch (2021), and in the Hideo Kojima video game Death Stranding (2019).