Sadako Yamamura is the main antagonist and central character in the Ringu film series. She is the vengeful ghost of a murdered teenage girl who seeks to get revenge against the entire world by projecting her essence into a cursed videotape that kills anyone who sees it.
She is the inspiration for the character Samara Morgan in The Ring, the American remake of the original film.
She is portrayed by Rie Inō in Ring and Ring 2, Hinako Saeki in Rasen, Yukie Nakama in Ring 0: Birthday, Ayane Miura in Ring: Kanzenban, Tae Kimura in the TV series Ring: The Final Chapter and Rasen, Ai Hashimoto in Sadako 3D, and Sadako 3D 2, Elly Nanami in Sadako vs Kayako, Jing-Wen Sun in Bunshinsaba vs Sadako, and Ru Yi in Bunshinsaba vs Sadako 2.