反乌托邦（英语：Dystopia、Cacotopia、kakotopia或anti-utopia，中文又称反面乌托邦、敌托邦、恶托邦、绝望乡或废托邦）是乌托邦（utopia）的反义语，希腊语字面意思是「不好的地方」（not-good place），它是一种不得人心、令人恐惧的假想社区或社会，是与理想社会相反的，一种极端恶劣的社会最终形态。反乌托邦常常表征为反人性（dehumanization）、 极权政府、生态灾难或其他社会性的灾难性衰败。这种社会出现在许多艺术作品中，特别是设置在未来的故事。反乌托邦出现在许多虚构作品的亚流派中，常被用于提醒人们注意现实世界中的有关环境、政治、经济、宗教、心理学、道德伦理、科学技术方面的问题，这些问题如果被人们忽略，有可能导致出现反乌托邦似的状况。

A dystopia (from the Greek δυσ- and τόπος, alternatively, cacotopia, kakotopia, or simply anti-utopia) is a community or society that is undesirable or frightening. It is translated as "not-good place", an antonym of utopia, a term that was coined by Sir Thomas More and figures as the title of his most well-known work, "Utopia." "Utopia" is the blueprint for an ideal society with no crime or poverty. Dystopian societies appear in many artistic works, particularly in stories set in the future. Some of the most famous examples are 1984 and Brave New World. Dystopias are often characterized by dehumanization, totalitarian governments, environmental disaster, or other characteristics associated with a cataclysmic decline in society. Dystopian societies appear in many subgenres of fiction and are often used to draw attention to real-world issues regarding society, environment, politics, economics, religion, psychology, ethics, science, and/or technology, which if unaddressed could potentially lead to such a dystopia-like condition.