A Wolf at the Door (Portuguese: O Lobo Atrás da Porta, lit. 'The Wolf Behind the Door') is a 2013 Brazilian thriller drama film written and directed by Fernando Coimbra, in his feature directorial debut. The film follows the story of Sylvia and Bernardo, the parents of a kidnapped girl, and Rosa, Bernardo's lover, who is suspected for the kidnapping. It is based on a real-life crime that occurred in the 1960s, where a woman named Neyde Maria Maia Lopes ("The Beast of Penha") kidnapped and killed four-year-old Tania Maria Coelho de Araujo ("Taninha").

The film had its world premiere at the 2013 Toronto International Film Festival. It won the Horizontes Latinos award at the 61st San Sebastián International Film Festival.