Cécile Crochon (French: [sesil kʁɔʃɔ̃]), better known by the stage name Cécile Cassel (born 25 June 1982), is a French actress and singer. Since 2002, she has appeared in a number of films and television series. She is also a recording artist using the stage name HollySiz.^[1]

She is the half-sister of actor Vincent Cassel and MC Mathias Cassel, and the daughter of Jean-Pierre Cassel.^[2] She has been in relationships with the French actor Gaspard Ulliel and the music producer Raphaël Hamburger.

• La Bande du drugstore (2002), directed by François Armanet : Charlotte Stroessman
• Vivante (2002), directed by Sandrine Ray : Isa
• A l'abri des regards indiscrets (2002), directed by Ruben Alves
• Nous étions libres (2004), directed by John Duigan : Céline Bessé
• Pour le plaisir (2004), directed by Dominique Deruddere : Mireille
• Foon (2005), of Benoît Pétré [fr]
• Ma vie en l'air (2005), of Rémi Bezançon : Clémence
• Contre-sens (2005), directed by Pierre-Alfred Richard
• Ô Jérusalem (2006), directed by Elie Chouraqui : Jane
• Les Amours d'Astrée et de Céladon (2007), directed by Éric Rohmer : Léonide
• Le Premier Jour du Reste de ta Vie (2008), directed by Rémi Bezançon : Prune
• Barbarossa (2009), Beatrice I, Countess of Burgundy
• Je vais te manquer (2009), Anna
• Toi, moi, les autres (2010), Alexandra
• Nuit bleue (2010), Antonia