Blood Tide is a 1982 British horror film directed by Richard Jefferies, and starring James Earl Jones, José Ferrer, Lila Kedrova, Lydia Cornell, Mary Louise Weller, Martin Kove, and Deborah Shelton. Its plot follows a young American couple visiting a Greek island where the husband's sister disappeared; they soon find that an ancient monster has been released, forcing the villagers to return to the practice of human sacrifice to appease it.

The film is also known as Bloodtide (in the US) and Demon Island (American TV title). It has been misconstrued as a public domain film and pirated by many distributors who copied it from DVDs. However, as per The Copyright Office, copyright is registered under Omega Entertainment, Inc. and the writer/producer of the film, Nico Mastorakis.