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Yūrei (幽霊) are figures in Japanese folklore, analogous to Western legends of ghosts. The name consists of two kanji, 幽 (yū), meaning "faint" or "dim" and 霊 (rei), meaning "soul" or "spirit." Alternative names include 亡霊 (Bōrei) meaning ruined or departed spirit, 死霊 (Shiryō) meaning dead spirit, or the more encompassing 妖怪 (Yōkai) or お化け (Obake).

Like their Chinese and Western counterparts, they are thought to be spirits kept from a peaceful afterlife. Yūrei do not wander at random, but generally stay near a specific location, such as where they were killed or where their body lies, or follow a specific person, such as their murderer, or a beloved. They usually appear between 2 and 3 a.m, the witching hour for Japan, when the veils between the world of the dead and the world of the living are at their thinnest.

Yūrei will continue to haunt that particular person or place until their purpose is fulfilled, and they can move on to the afterlife. However, some particularly strong yūrei, specifically onryō who are consumed by vengeance, continue to haunt long after their killers have been brought to justice.

Some famous locations that are said to be haunted by yūrei are the well of Himeji Castle, haunted by the ghost of Okiku, and Aokigahara, the forest at the bottom of Mt. Fuji, which is a popular location for suicide. A particularly powerful onryō, Oiwa, is said to be able to bring vengeance on any actress portraying her part in a theater or film adaptation.

While all Japanese ghosts are called yūrei, within that category there are several specific types of phantom, classified mainly by the manner they died or their reason for returning to Earth.

Onryō - Vengeful ghosts who come back from purgatory for a wrong done to them during their lifetime.

Ubume - A mother ghost who died in childbirth, or died leaving young children behind. This yūrei returns to care for her children, often bringing them sweets.

Goryō - Vengeful ghosts of the aristocratic class, especially those who were martyred.

Funayūrei - The ghosts of those who died at sea. These ghosts are sometimes depicted as scaly fish-like humanoids and some may even have a form similar to that of a mermaid or merman.

Zashiki-warashi - The ghosts of children, often mischievous rather than dangerous.

Samurai Ghosts - Veterans of the Genpei War who fell in battle. Warrior Ghosts almost exclusively appear in Noh Theater. Unlike most other yūrei, these ghosts are usually shown with legs.

Seductress Ghosts - The ghost of a woman or man who initiates a post-death love affair with a living human.

The easiest way to exorcise a yūrei is to help it fulfill its purpose. When the reason for the strong emotion binding the spirit to Earth is gone, the yūrei is satisfied and can move on. Traditionally, this is accomplished by family members enacting revenge upon the yūrei's slayer, or when the ghost consummates its passion/love with its intended lover, or when its remains are discovered and given a proper burial with all rites performed.

The emotions of the onryō are particularly strong, and they are the least likely to be pacified by these methods.

On occasion, Buddhist priests and mountain ascetics were hired to perform services on those whose unusual or unfortunate deaths could result in their transition into a vengeful ghost, a practice similar to exorcism. Sometimes these ghosts would be deified in order to placate their spirits.

Like many monsters of Japanese folklore, malicious yūrei are repelled by ofuda (御札), holy Shinto writings containing the name of a kami. The ofuda must generally be placed on the yūrei's forehead to banish the spirit, although they can be attached to a house's entry ways to prevent the yūrei from entering.