Emasculation is the removal of the external male sex organs, which includes both the penis and the scrotum, the latter of which contains the testicles. It is distinct from castration, where only the testicles are removed. Although the terms are sometimes used interchangeably, the potential medical consequences of emasculation are more extensive due to the complications arising from the removal of the penis. There are a range of religious, cultural, punitive, and personal reasons why someone may choose to emasculate themself or another person.

The term emasculation may be used in a metaphorical sense, referring to the perceived loss of attributes traditionally associated with masculinity, such as strength, power, or autonomy.

There are several different methods of emasculation. Both the penis and testicles may be removed simultaneously using a sharp instrument, such as a knife or razor or swords. Non-crushing vascular clamps may also be used in medical surgery to cut off blood circulation and reduce bleeding.

Short-term consequences of emasculation include bleeding and infection. Historically, death was also a potential complication, although the prevalence is disputed.

Long term complications include incontinence, urethral stricture, urine retention, urinary tract infection, urine extravasation and bladder stones. Some studies have found that emasculation may cause a range of physiological changes, such as a shortened torso, widened stomach and hips, increased height, bowed legs, and an elongated skull. Additionally, emasculates typically have less or no facial and body hair, increased fatty tissue or gynecomastia, and a feminine fat pattern distribution. The physiological effects of emasculation are more severe for people who undergo the procedure before the onset of puberty.

Emasculation was performed in China on men to create palace eunuchs for the imperial court. The practice dates back to the Shang dynasty (1600–1046 BC) and continued up until 1924, when the eunuch system was abolished by the last emperor of China, Puyi. The last living palace eunuch, Sun Yaoting, died in 1996.

Originally, palace eunuchs were prisoners who were involuntarily emasculated. In the Qing dynasty, men began volunteering to undergo the procedure in order to gain employment, although instances of forced emasculation still occurred. One reason why recipients willingly underwent emasculation is that they saw employment as a palace eunuch as a way to acquire wealth and power. Alternatively, poverty was a reason why fathers forced their sons to undergo emasculation, and the desire for financial benefit motivated human traffickers to force emasculation on their victims.

There were several reasons why the Imperial court required its civil servants to be emasculated. Emasculation was thought to ensure a recipient's undivided loyalty to the emperor, as it severs the recipient's existing familial or social bonds and destroys their ability to produce future heirs. The choice to hire emasculated eunuchs also ensured the legitimacy of the emperor's lineage. The choice to emasculate, rather than merely castrate, was motivated by a desire to protect the chastity of women in the court, as emasculation rendered a recipient incapable of sexual intercourse. While emasculation was a pre-requisite for gaining employment as a palace eunuch, it did not guarantee employment.