An autopsy (also referred to as post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death; or the exam may be performed to evaluate any disease or injury that may be present for research or educational purposes. The term necropsy is generally used for non-human animals.

Autopsies are usually performed by a specialized medical doctor called a pathologist. Only a small portion of deaths require an autopsy to be performed, under certain circumstances. In most cases, a medical examiner or coroner can determine the cause of death.

Autopsies are performed for either legal or medical purposes. Autopsies can be performed when any of the following information is desired:

For example, a forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes. Autopsies can be further classified into cases where an external examination suffices, and those where the body is dissected and an internal examination is conducted. Permission from next of kin may be required for internal autopsy in some cases. Once an internal autopsy is complete, the body is reconstituted by sewing it back together.

The term "autopsy" derives from the Ancient Greek αὐτοψία autopsia, "to see for oneself", derived from αὐτός (autos, "oneself") and ὄψις (opsis, "sight, view"). The word has been in use since around the 17th century.

The term "post-mortem" derives from the Latin post, 'after', and mortem, 'death'. It was first recorded in 1734.

The term "necropsy" is derived from the Greek νεκρός (nekrós, "dead") and ὄψις (opsis, 'sight, view').

The principal aims of an autopsy are to determine the cause of death, mode of death, manner of death, the state of health of the person before he or she died, and whether any medical diagnosis and treatment before death were appropriate. In most Western countries the number of autopsies performed in hospitals has been decreasing every year since 1955. Critics, including pathologist and former JAMA editor George D. Lundberg, have charged that the reduction in autopsies is negatively affecting the care delivered in hospitals, because when mistakes result in death, they are often not investigated and lessons, therefore, remain unlearned. When a person has permitted an autopsy in advance of their death, autopsies may also be carried out for the purposes of teaching or medical research. An autopsy is usually performed in cases of sudden death, where a doctor is not able to write a death certificate, or when death is believed to result from an unnatural cause. These examinations are performed under a legal authority (medical examiner, coroner, or procurator fiscal) and do not require the consent of relatives of the deceased. The most extreme example is the examination of murder victims, especially when medical examiners are looking for signs of death or the murder method, such as bullet wounds and exit points, signs of strangulation, or traces of poison. Some religions including Judaism and Islam usually discourage the performing of autopsies on their adherents. Organizations such as ZAKA in Israel and Misaskim in the United States generally guide families on how to ensure that an unnecessary autopsy is not made. Autopsies are used in clinical medicine to identify a medical error or a previously unnoticed condition that may endanger the living, such as infectious diseases or exposure to hazardous materials. A study that focused on myocardial infarction (heart attack) as a cause of death found significant errors of omission and commission, i.e. a sizable number of cases ascribed to myocardial infarctions (MIs) were not MIs and a significant number of non-MIs were MIs.