Petra Schmidt-Schaller is a German actress. She is noted for the roles of Helene in Runaway Horse alongside Ulrich Noethen, Ulrich Tukur and Katja Riemann, and Maud Brewster in The Sea Wolf alongside Thomas Kretschmann.

Unknown is a 2011 action-thriller film directed by Jaume Collet-Serra and starring Liam Neeson, Diane Kruger, January Jones, Aidan Quinn, Bruno Ganz, and Frank Langella. The film, produced by Joel Silver, Leonard Goldberg and Andrew Rona, is based on the 2003 French novel by Didier Van Cauwelaert published in English as Out of My Head which was adapted as the film's screenplay by Oliver Butcher and Stephen Cornwell. The narrative centers around a professor who wakes up from a four-day long coma and sets out to prove his identity after no one recognizes him, including his own wife, and another man claims to be him.