The Keep is a 1983 supernatural horror film written and directed by Michael Mann and starring Scott Glenn, Gabriel Byrne, Jürgen Prochnow, Alberta Watson, and Ian McKellen. Set in Romania during World War II, it follows a group of Nazi soldiers who unleash a malevolent supernatural force after setting up camp in an ancient stone fortress in the Carpathian Mountains. It is an adaptation of the 1981 novel of the same title by American writer F. Paul Wilson. The musical score was composed by Tangerine Dream.

Michael Kenneth Mann is an American film director, screenwriter, author, and producer, best known for his stylized crime dramas. Mann has received numerous accolades including a BAFTA Award and two Primetime Emmy Awards as well as nominations for four Academy Awards and two Golden Globe Awards. His most acclaimed works include the films Thief (1981), Manhunter (1986), The Last of the Mohicans (1992), Heat (1995), The Insider (1999), Ali (2001), Collateral (2004), Public Enemies (2009), and Ferrari (2023). He is also known for his role as executive producer on the popular TV series Miami Vice (1984–90), which he adapted into a 2006 feature film.