Necrophilia, also known as necrophilism, necrolagnia, necrocoitus, necrochlesis, and thanatophilia, is sexual attraction or acts involving corpses, including both direct intercourse with corpses and sexual excitement at the thought or presence of one. It is classified as a paraphilia by the World Health Organization (WHO) in its International Classification of Diseases (ICD) diagnostic manual, as well as by the American Psychiatric Association in its Diagnostic and Statistical Manual (DSM). Reported motivations vary widely, ranging between sexual domination of a non-responsive partner, fetishization of death and corpses, and bereavement of a close sexual partner. Necrophilia can coincide with sexual roleplay of the subject instead pretending to be a corpse while their partner takes on the role of the necrophile.

In contrast to human paraphilias, many cases of animal necrophilia (also known as Davian behavior) have been observed, primarily as a result of being unable to distinguish between a receptive mate and a recently deceased one. Some species of arthropods and frogs can instead fully copulate with a recently killed mate.

Various terms for the crime of corpse violation animate seventeenth- through nineteenth-century works on law and legal medicine. The plural term "nécrophiles" was coined by Belgian physician Joseph Guislain in his lecture series, Leçons Orales Sur Les Phrénopathies, given around 1850, about the contemporary necrophiliac François Bertrand:

It is within the category of the destructive madmen [aliénés destructeurs] that one needs to situate certain patients to whom I would like to give the name of necrophiliacs [nécrophiles]. The alienists have adopted, as a new form, the case of Sergeant Bertrand, the disinterred of cadavers on whom all the newspapers have recently reported. However, don't think that we are dealing here with a form of phrenopathy that appears for the first time. The ancients, in speaking about lycanthropy, have cited examples to which one can more or less relate the case which has just now attracted the public attention so strongly.

Psychiatrist Bénédict Morel popularised the term about a decade later when discussing Bertrand.

In the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, Text Revision (DSM-5-TR), recurrent, intense sexual interest in corpses can be diagnosed under Other Specified Paraphilic Disorder (necrophilia) when it causes marked distress or impairment in important areas of functioning.

Forensic Psychologist Anil Aggrawal introduced a ten-tier classification of necrophiliacs based on the increasing severity of the disorder.

In the ancient world, sailors returning corpses to their home country were often accused of necrophilia. Singular accounts of necrophilia in history are sporadic, though written records suggest the practice was present within Ancient Egypt. Herodotus writes in The Histories that, to discourage intercourse with a corpse, ancient Egyptians left deceased beautiful women to decay for "three or four days" before giving them to the embalmers. Herodotus also alluded to suggestions that the Greek tyrant Periander had defiled the corpse of his wife, employing a metaphor: "Periander baked his bread in a cold oven." Acts of necrophilia are depicted on ceramics from the Moche culture, which reigned in northern Peru from the first to eighth-century CE. A common theme in these artifacts is the masturbation of a male skeleton by a living woman. Hittite law from the 16th century BC through to the 13th century BC explicitly permitted sex with the dead. In what is now Northeast China, the ethnic Xianbei emperor Murong Xi (385–407) of the Later Yan state had intercourse with the corpse of his beloved empress Fu Xunying after the latter was already cold and put into the coffin.