Cosima Ertl is a German voice actor and actress based in Hamburg, recognized for her work in dubbing foreign-language films and series into German, as well as for her performances on stage and in audio dramas. She is bilingual, speaking both German and English fluently, and her vocal profile is characterized as bright, warm, and believable, allowing her to portray a wide range of characters from children and teenagers to adults.

Her path to voice acting is built on a foundation of both practical industry experience and extensive performance training. Ertl worked for several years in the dubbing industry as a translator, subtitler, and project manager at VSI Synchron GmbH in Berlin from 2007 to 2011. This behind-the-scenes work provided her with deep insight into the localization process before she focused on her performing career. She has also pursued continuous professional development, taking numerous courses in dubbing, voice acting, and camera acting from respected coaches in Berlin and Hamburg. Earlier in her career, she studied theatre for a year at Illinois College in the United States.

Ertl has accumulated a significant number of voice roles in German dubs, with one database listing 42 speaking roles. Her work spans both animation and live-action productions. In anime, she is known for providing the German voice for the character Lirio in the series El Cazador de la Bruja. Her other notable anime dubbing credits include roles in Code Geass: Lelouch of the Rebellion, Claymore, Sweet Reincarnation as Licorice Mille Hubarek, Reign of the Seven Spellblades as Stacy Cornwallis, Boruto: Naruto Next Generations as Hako Kuroi, Die Tagebücher der Apothekerin as Rifa, and The Ancient Magus' Bride as Sofia. Beyond anime, her work encompasses a wide variety of international series and films, such as providing the German voice for characters in Yellowstone, The Winchesters, Tokyo Vice, and the film Topside - Flucht ins Ungewisse.

In addition to her voice work for screen dubs, Ertl is active in audio dramas and radio plays. She has voiced characters for popular German audio series like Feuerwehrmann Sam, TKKG junior, and Die drei!!!, as well as the Asterix audio drama Die Weisse Iris. She also has a strong background in theatre and musical performance, having appeared in numerous stage productions in Berlin and beyond, with roles ranging from classical plays like Bertolt Brecht's The Wedding to original musicals where she also contributed as a writer. Her experience extends to on-camera work, including a lead role and screenwriting credit for the 2024 short film A Bit of Fun. She frequently collaborates with her identical twin sister, Corinna Ertl, an animator and motion designer, by providing narration and character voices for Corinna's animated projects.