The word ryona (リョナ, ryona; a blend of ryōki ("seeking the bizarre") and onanī ("masturbation")) is a type of sexual fetish in hentai wherein a protagonist is subject to sexual, physical, or psychological abuse from an offender. The term is mostly used in connection to Japanese culture, although the themes of misogyny, sadomasochism, compassion, exoticism, and extreme erotica is seen in many other cultures.

The term ryona almost exclusively refers to the action of a distressed woman being abused and dominated by men at an extreme level as its narrative centerpiece. In a case where the target is male, it is more commonly called gyaku-ryona (逆リョナ, gyaku-ryona; "reverse ryona"), and generally implies content with a female assailant and a male victim. The genre focuses exclusively on fictional characters in these situations. In some cases, the perpetrator could be a monster or other non-human being.

Because the fetish is very broad in scope, it often contrasted with or incorporates other, more common, fetishes such as humiliation, sexual sadism, and rape pornography, in that ryona is a complex and nuanced voyeuristic fantasy fetish, a romanticized subgenre aimed at a female target demographic and are almost always of non-explicit sexual nature. Unlike the genre of guro (グロ) or Ero guro (エログロ), ryona never progresses to the point of death or lasting physical harm.

Works in the ryona genre usually depict two characters meeting and developing a relationship with each other, which may begin in or devolve into a state of hostility.

The nature of abuse can vary greatly, but it usually includes one or more of the following:

• Domestic violence and rape, and depictions thereof
• Inconvenient disruption of everyday life, such as being prevented from attending one's job, or being embarrassed or rejected by friends and family
• Forced confinement and detention for extended periods of time
• Literal torture for extortion, confession, or simply for sexual gratification of the torturer.
• Murder and necrophilia for sexual pleasure.
• Being regarded and treated as property of another person

• Mook, Sanwa (2013). 本当に正しいフェティシズム性的嗜好大事典 [Honto ni Tadashi Fetishizumu Seiteki Shiko Daijiten] [Really Right Fetish: A Taste of Large Dictionary] (in Japanese). Sanwa Shuppan. ISBN 9784776910701. OCLC 870402367.