A crucifix (from the Latin cruci fixus meaning '(one) fixed to a cross') is a cross with an image of Jesus on it, as distinct from a bare cross. The representation of Jesus himself on the cross is referred to in English as the corpus (Latin for 'body').

The crucifix is a principal symbol for many groups of Christians, and one of the most common forms of the Crucifixion in the arts. It is especially important in the Roman Rite of the Roman Catholic Church, but is also used in the Eastern Orthodox Church, most Oriental Orthodox Churches (except the Armenian & Syriac Church), and the Eastern Catholic Churches, as well as by the Lutheran, Moravian and Anglican Churches. The symbol is less common in churches of other Protestant denominations, and in the Assyrian Church of the East and Armenian Apostolic Church, which prefer to use a cross without the figure of Jesus (the corpus). The crucifix emphasizes Jesus' sacrifice—his death by crucifixion, which Christians believe brought about the redemption of humankind. Most crucifixes portray Jesus on a Latin cross, rather than any other shape, such as a Tau cross or a Coptic cross.

Roman Catholics see the crucifix as the perfect fulfillment of that inferred by the serpent created by Moses in Numbers 21:8—9, called the Nehushtan. It was promised that those sinners who looked upon the Nehushtan would be healed. The section of Numbers about the Nehushtan is one of the readings on Exaltation of the Cross that occurs on September 14 in the Roman Catholic Church. It is paired with John 3:14–15 as the gospel reading. Taken together, these readings explain the striking front and center position of a large crucifix normally fixed above or behind a Catholic altar.

Western crucifixes usually have a three-dimensional corpus, but in Eastern Orthodoxy Jesus' body is normally painted on the cross, or in low relief. Strictly speaking, to be a crucifix, the cross must be three-dimensional, but this distinction is not always observed. An entire painting of the crucifixion of Jesus including a landscape background and other figures is not a crucifix either.

Large crucifixes high across the central axis of a church are known by the Old English term rood. By the Late Middle Ages these were a near-universal feature of Western churches, but they are now very rare. Modern Roman Catholic churches and many Lutheran churches often have a crucifix above the altar on the wall; for the celebration of Mass, the Roman Rite of the Catholic Church requires that "on or close to the altar there is to be a cross with a figure of Christ crucified".