In Japanese traditional beliefs and literature, onryō (怨霊, literally "vengeful spirit", sometimes rendered "wrathful spirit") refers to a ghost (yūrei) believed to be capable of causing harm in the world of the living, injuring or killing enemies, or even causing natural disasters to exact vengeance to redress the wrongs it received while alive, then taking their spirits from their dying bodies.
While the origin of onryō is unclear, belief in their existence can be traced back to the 8th century and was based on the idea that powerful and enraged souls of the dead could influence or harm the living. The earliest onryō cult that developed was around Prince Nagaya who died in 729; and the first record of possession by the onryō spirit affecting health is found in the chronicle Shoku Nihongi (797), which states that "Fujiwara Hirotsugu (藤原広嗣)'s soul harmed Genbō to death" (Hirotsugu having died in a failed insurrection, named the "Fujiwara no Hirotsugu Rebellion", after failing to remove his rival, the priest Genbō, from power).
Traditionally in Japan, onryō driven by vengeance were thought capable of causing not only their enemy's death, as in the case of Hirotsugu's vengeful spirit held responsible for killing the priest Genbō, but causing natural disasters such as earthquakes, fires, storms, drought, famine and pestilence, as in the case of Prince Sawara's spirit embittered against his brother, the Emperor Kanmu. In common parlance, such vengeance exacted by supernatural beings or forces is termed tatari (祟り).
The Emperor Kanmu had accused his brother Sawara, possibly falsely, of plotting to remove him as rival to the throne, and the latter who was exiled died by fasting. The reason that the Emperor moved the capital to Nagaoka-kyō thence to Kyoto was an attempt to avoid the wrath of his brother's spirit, according to a number of scholars. This not succeeding entirely, the emperor tried to lift the curse by appeasing his brother's ghost, by performing Buddhist rites to pay respect, and granting Prince Sawara the posthumous title of emperor.
A well-known example of appeasement of the onryō spirit is the case of Sugawara no Michizane, who had been politically disgraced and died in exile. It was believed to cause the death of his calumniators in quick succession, as well as catastrophes (especially lightning damage), and the court tried to appease the wrathful spirit by restoring Michizane's old rank and position. Michizane became deified in the cult of the Tenjin, with Tenman-gū shrines erected around him.
Possibly the most famous onryō is Oiwa, from the Yotsuya Kaidan. In this story the husband remains unharmed; however, he is the target of the onryō’s vengeance. Oiwa's vengeance on him isn't physical retribution, but rather psychological torment.
Other examples include:
- How a Man's Wife Became a Vengeful Ghost and How Her Malignity Was Diverted by a Master of Divination
- In this tale from the medieval collection, Konjaku Monogatarishū, an abandoned wife is found dead with a full head of hair intact and the bones still attached. The husband, fearing retribution from her spirit, asks a diviner (陰陽師 onmyōji) for aid. The husband must endure while grabbing her hair and riding astride her corpse. She complains of the heavy load and leaves the house to "go looking" (presumably for the husband), but after a day she gives up and returns, after which the diviner is able to complete her exorcism with an incantation.
- Of a Promise Broken
- In this tale from the Izumo area recorded by Lafcadio Hearn, a samurai vows to his dying wife never to remarry. He soon breaks the promise, and the ghost comes to first warn, then murder the young bride, ripping her head off. The watchmen who had been put to sleep chase down the apparition, and with a slash of the sword while reciting Buddhist prayer, destroy it.
The onryō is a staple of the J-Horror genre, most notable being Sadako Yamamura and Kayako Saeki from the Ring and Ju-On franchises, respectively. The characters in these works are almost exclusively women who were wronged in life, returning as onryō to wreak havoc on the living and ultimately be reborn.
Hisako (久子, "Eternal Child" or "Everlasting Child") from the third entry of the fighting game Killer Instinct, is an onryō who died while defending her village. She still haunts her old village and will take vengeance on anyone who desecrates its ruins with her naginata. She has pale white skin and long black hair like most onryō. 
The ghost form of Cynthia Velasquez from the survival horror game Silent Hill 4: The Room closely resembles onryō.
In fall 2018, the asymmetrical horror game Dead by Daylight released the Shattered Bloodline chapter DLC, and with it came Rin Yamaoka, The Spirit. The Spirit is an onryō who returns from the dead after being brutally murdered by her father.
Highly visual in nature, and with a single actor often assuming various roles within a play, Kabuki developed a system of visual shorthand that allowed the audience to instantly clue in as to which character is on stage, as well as emphasize the emotions and expressions of the actor.
A ghost costume consisted of three main elements:
- White burial kimono, shiroshōzoku (白装束) or shinishōzoku (死に装束)
- Wild, unkempt long black hair
- Face make-up consisting of white foundation (oshiroi) coupled with face paintings (kumadori) of blue shadows (藍隈 aiguma) "indigo fringe", much like villains are depicted in kabuki make-up artistry.[a]
- Grappard, Allan G. (1988), "Religious practices", in Hall, John Whitney (ed.), The Cambridge History of Japan, 2, pp. 559–, ISBN 978-0521223539
- For a source that identifies Hirotsugu as onryō, see:Suzuki 2011, 135 (note 2 to Chapter 2)
- A source that gives Hirotsugu as first example on record of "etiological possession" is McCullough 1973, p. 97
- McCullough, William H. (1973), Ōta, Saburo (太田三郎); Fukuda, Rikutaro (福田陸太郎) (eds.), "Spirit Possession in the Heian Period", Studies on Japanese Culture (日本文化研究論集), 1: 97; (Also printed in Nihon Bunka Kenkyū Kokusai Kaigi gijiroku (日本文化研究国際会議議事錄) (Volume 1, 1973, pp. 350- (p.356)
- Suzuki, Yui (2011). Medicine Master Buddha: The Iconic Worship of Yakushi in Heian Japan. BRILL. pp. 29–31. ISBN 978-9004196018.
- Jones, S. W. (translator), ed. (1959). Ages ago; thirty-seven tales from the Konjaku monogatari collection (snippet). Harvard University Press. p. 72.
- One of the texts cited by Jones: Haga, Yaichi (芳賀矢一), ed. (1921), 攷証今昔物語集 (Kōshō konjaku monogatari shū), 3 (下), p. 106 Missing or empty
- Hearn, Lafcadio (1901), "Of a Promise Broken", A Japanese miscellany, Little, Brown, pp. 15–26
- 日本博学倶楽部 (2005). 「通」になれる古典芸能を楽しむ本: 落語・歌舞伎から能・狂言まで. PHP研究所. p. 57. ISBN 978-4569665498.
- Parker, Helen S. E. (2006). Progressive Traditions: An Illustrated Study of Plot Repetition In Traditional Japanese Theatre. BRILL. p. 87. ISBN 978-9004145344.