Ring 0: Birthday (リング0 バースデイ, Ringu Zero: Bāsudei) is a 2000 Japanese supernatural psychological thriller film directed by Norio Tsuruta, from a screenplay by Hiroshi Takahashi, based on the short story "Lemon Heart" from the Birthday anthology by Koji Suzuki. A prequel to Ring (1998), the story follows the life of the character of Sadako Yamamura just before she consigned to her fate seen in the later Ring series.

Ring 0, along with Isola was known for being the one of the earliest Japanese live-action psychological thriller-focused films to be released theatrically. as well as the first psychological thriller films which released theatrically in Japan during early 2000s to gross over ¥1 billion in distribution income, preceding other releases like The Beach, Unbreakable, Vanilla Sky and Panic Room. Ring 0: Birthday was nominated for the 2001 edition of Fantasporto, but lost to Amores perros.