Jehovah's Witnesses is a millenarian restorationist Christian denomination with nontrinitarian beliefs distinct from mainstream Christianity. The religion reports worldwide membership of over 7 million adherents involved in evangelism; they report convention attendance of over 12 million, and annual Memorial attendance of over 18 million. They are directed by a Governing Body of elders which exercises authority on all doctrinal matters. Witnesses base their beliefs on the Bible, and prefer their own translation, the New World Translation of the Holy Scriptures.

The group emerged from the Bible Student movement, founded in the late 19th century by Charles Taze Russell, with the formation of Zion's Watch Tower Tract Society. Following a schism in the movement, the branch that maintained control of the Society underwent significant organizational changes, bringing its authority structure and methods of evangelism under centralized control. The name Jehovah's witnesses, based on Isaiah 43:10–12, was adopted in 1931.

Since its inception, the Watch Tower Society has taught that the present world order is in its last days and will soon be destroyed at Armageddon. It has stated that only Jehovah's Witnesses "have any Scriptural hope of surviving the impending end of this doomed system", but that God decides who will survive. Those whom God chooses to save—survivors and resurrected individuals—will have the opportunity to live forever in an earthly paradise, ruled by Christ and 144,000 humans raised to heaven. In the years leading up to 1914, 1925 and 1975, the Watch Tower Society's publications expressed strong expectations of Armageddon or the establishment of Christ's kingdom over the earth occurring in those years.

Jehovah's Witnesses are best known for their door-to-door preaching, distribution of literature such as The Watchtower and Awake!, and for their refusal of military service and blood transfusions even in life-threatening situations. They consider use of the name Jehovah—or other common-language pronunciations of the Tetragrammaton—vital for proper worship. They reject Trinitarianism, immortality of the soul, and hellfire, which they consider to be unscriptural doctrines. They do not observe celebrations such as Christmas, Easter or birthdays, which they believe have pagan origins that are not compatible with Christianity. Members commonly refer to their body of beliefs as "the Truth", and adherents consider themselves to be "in the Truth". Jehovah's Witnesses regard secular society as a place of moral contamination under the influence of Satan, and limit their social interaction with non-Witnesses.

Baptized members who violate the organization's fundamental moral principles or who dispute doctrinal matters can be subject to disciplinary action. Members who are considered unrepentant after counseling may be subject to a form of shunning called disfellowshipping. Members who formally announce their resignation from the religion are also shunned.

The religion's position regarding conscientious objection to military service and refusal to salute national flags has brought it into conflict with governments, particularly those that conscript citizens for military service. Consequently, activities of Jehovah's Witnesses have been banned or restricted in some countries. Persistent legal challenges by Jehovah's Witnesses have had considerable influence on related legislation and civil rights in the United States and other countries.