Exorcism (from Ancient Greek ἐξορκισμός (exorkismós) 'binding by oath') is the religious or spiritual practice of evicting demons, jinns, or other malevolent spiritual entities from a person, or an area, that is believed to be possessed. Depending on the spiritual beliefs of the exorcist, this may be done by causing the entity to swear an oath, performing an elaborate ritual, or simply by commanding it to depart in the name of a higher power. The practice is ancient and part of the belief system of many cultures and religions.

In Christianity, exorcism is the practice of casting out or getting rid of demons. In Christian practice, the person performing the exorcism, known as an exorcist, is a member of a Christian Church, or an individual thought to be graced with special powers or skills. The exorcist may use prayers and religious material, such as set formulae, gestures, symbols, sacred images, sacramentals, etc. The exorcist often invokes God, Jesus or several different angels and archangels to intervene with the exorcism. Protestant Christian exorcists most commonly believe the authority given to them by the Father, Son, and Holy Spirit (the Trinity) is the sole source of their ability to cast out demons.

In general, people considered to be possessed are not regarded as evil unto themselves, nor wholly responsible for their actions, because possession is considered to be the unwilling manipulation by a demon resulting in harm to self or others. Therefore, practitioners regard exorcism as more of a cure than a punishment. The mainstream rituals usually take this into account, making sure that there is no violence to the possessed, only that they be tied down if there is potential for violence.

Requested and performed exorcisms began to decline in the United States by the 18th century, and occurred rarely until the latter half of the 20th century when the public saw a sharp rise due to the media attention exorcisms received. There was "a 50% increase in the number of exorcisms performed between the early 1960s and the mid-1970s".

In Catholicism, exorcisms are performed in the name of Jesus Christ. There is a distinction between major exorcisms and minor exorcisms. Minor exorcisms are included in some blessings in which priests create sacramentals, such as blessed salt, and are also found in the ritual Scrutinies of the catechumens. A related practice is deliverance ministry. The distinction between deliverance ministry and exorcism is that exorcism is conducted by priests given special permission from the Catholic Church, while deliverance ministry is prayer for people who are distressed and wish to heal emotional wounds, including those purportedly caused by evil spirits.

The Catholic rite for a formal exorcism, called a "Major Exorcism", is given in Section 11 of the Rituale Romanum. The Ritual lists guidelines for conducting an exorcism and determining when a formal exorcism is required. Priests are instructed to carefully determine that the nature of the condition is not actually a psychological or physical illness before proceeding. The United States Conference of Catholic Bishops state on their website: "the actual determination of whether a member of the faithful is genuinely possessed by the devil is made by the Church."

In Catholic practice, the person performing the exorcism, known as an exorcist, must be an ordained priest. The exorcist recites prayers according to the rubrics of the rite, and makes use of religious materials such as icons, sacramentals (e.g. holy water), and holy relics. The exorcist invokes God—specifically the Name of Jesus Christ—as well as the Most Blessed Virgin Mary, saints of the Church Triumphant and the Archangel Michael to intervene with the exorcism. According to Catholic understanding, several weekly exorcisms over many years are sometimes required to expel a deeply entrenched demon.

Saint Michael's Prayer against Satan and the Rebellious Angels, attributed to Pope Leo XIII, is considered the strongest prayer of the Catholic Church against cases of diabolic possession. The Holy Rosary also has an exorcistic and intercessory power.