Blood of Christ, also known as the Most Precious Blood, in Christian theology refers to the physical blood actually shed by Jesus Christ primarily on the Cross, and the salvation which Christianity teaches was accomplished thereby, or the sacramental blood (wine) present in the Eucharist or Lord's Supper, which some Christian denominations believe to be the same blood of Christ shed on the Cross.

The Roman and Eastern Catholic Churches, Eastern Orthodox Church, the Oriental Orthodox churches, the Assyrian and Ancient Churches of the East, and Lutherans, together with high church Anglicans, know this as the real presence of Christ in the Eucharist. The Catholic Church uses the term transubstantiation to describe the change of the bread and wine into the body and blood of Christ. The Eastern Orthodox Churches used the same term to describe the change, as in the decrees of the 1672 Synod of Jerusalem, and the Catechism of St. Philaret (Drozdov) of Moscow.

The Lutheran churches follow the teaching of Martin Luther in defining the presence of Christ in the eucharistic elements as sacramental union (often misconstrued as consubstantiation), meaning that the fundamental "substance" of the body and blood of Christ are literally present alongside the substance of the bread and wine, which remain present. Lutherans too believe in and teach the Real Presence. Other Protestant churches reject the idea of the Real Presence; they observe eucharistic rites as simply memorials.