in Christianity, the change by which the substance (though not the appearance) of the bread and wine in the Eucharist becomes Christ's Real Presence—that is, his body and blood. In Roman Catholicism and some other Christian churches the doctrine, which was first called transubstantiation in the 12th century, aims at safeguarding the literal truth of Christ's Presence while emphasizing the fact that there is no change in the empirical appearances of the bread and wine.

The doctrine of transubstantiation, elaborated by scholastic theologians from the 13th to the 15th century, was incorporated into the documents of the Council of Trent (Trent, Council of) (1545–63). The faith in the Real Presence as brought about by a mysterious change antedates the scholastic formulation of the doctrine, as is shown by the use of equivalent terms in the patristic writers. In the mid-20th century some Roman Catholic theologians restated the doctrine of Christ's eucharistic presence. Shifting the emphasis from a change of substance to a change of meaning, they coined the terms transsignification and transfinalization to be used in preference to transubstantiation. But, in his encyclical Mysterium fidei in 1965, Pope Paul VI called for a retention of the dogma of Real Presence together with the terminology of transubstantiation in which it had been expressed.