不死生物（英语：undead），又称不死族、亡灵族、死灵族，是指肉体已经死亡却还能活动的怪物，通常被认为是遗留人间的魂魄和具自我意识的尸体。不死生物以不同的型态出现在各地文化的传说中和小说里，通常在奇幻小说、恐怖小说和角色扮演游戏中出现。

The undead are beings in mythology, legend, or fiction that are deceased but behave as if alive. A common example of an undead being is a corpse re-animated by supernatural forces, by the application of the deceased's own life force, or that of another being (such as a demon). The undead may be incorporeal like ghosts, or corporeal like vampires and zombies. The undead are featured in the belief systems of most cultures, and appear in many works of fantasy and horror fiction.