The epiclesis (also spelled epiklesis; from Ancient Greek: ἐπίκλησις, lit. 'surname' or 'invocation') refers to the invocation of one or several gods. In ancient Greek religion, the epiclesis was the epithet used as the surname given to a deity in religious contexts. The term was borrowed into the Christian tradition, where it designates the part of the Anaphora (Eucharistic Prayer) by which the priest invokes the Holy Spirit (or the power of God's blessing) upon the Eucharistic bread and wine in some Christian churches. In most Eastern Christian traditions, the Epiclesis comes after the Anamnesis (remembrance of Jesus' words and deeds); in the Western Rite it usually precedes. In the historic practice of the Western Christian Churches, the consecration is effected at the Words of Institution, though during the rise of the Liturgical Movement, many denominations introduced an explicit epiclesis in their liturgies.

The Ancient Greek term epíklēsis (ἐπίκλησις; literally 'calling upon') can be translated as 'surname, additional name', or as 'invocation, appeal'.

In ancient Greek religion, the epiclesis was used as the surname that was associated with a deity during religious invocations, in contrast to the more general term 'epithet' (ἐπίθετον), which is used in poetic contexts. In the 2nd century AD, the Greek geographer Pausanias used the term 'epiclesis' to designate the appellation under which a deity was honoured in specific places or occasions.

In 2001, in the Pontifical Council for Promoting Christian Unity on admission to the Eucharist between Chaldean Catholic Church and Assyrian Church of the East issued a statement stating that the Words of Institution are dispersed euchologically in the Liturgy of Addai and Mari, wherein the words are stated not in immediate sequence but throughout the Liturgy. The Eastern Orthodox Churches hold the Epiclesis to be the moment at which this change is completed. However, the actual process of change is not considered to begin at this moment, but rather to have begun with the Liturgy of Preparation—it is merely completed at the Epiclesis.

In the 20th century, when Western Rite Orthodox parishes began to be established, liturgies were derived from Catholic Latin liturgical rites and the Anglican Book of Common Prayer. These liturgies saw a "stronger" Epiclesis inserted, as to better align them with the Byzantine liturgy.

In the Liturgy of St. Cyril (also known as Egyptian Liturgy of St. Mark), the Epiclesis typically appears after the post-sanctus prayer. The structure is usually as follows: Epiclesis I—Institution Narrative—Anamnesis—Epiclesis II. Since these group of liturgies contain the earliest full anaphoras available to us, they have become incredibly important in understanding the development of liturgical prayers. The epicleses of these anaphora are seen as consecratory; however, recent papers have shown that the liturgical thought of Egypt was less focused on a specific moment of consecration, being more process-focused in terms of Eucharistic Consecration.

In its pure form, the ancient anaphora of the Liturgy of Addai and Mari used in the Church of the East (East Syriac Rite) does include an epiclesis. It does not use the Words of Institution, although they appear directly and indirectly in other parts of the rite (and is therefore considered to be implicit).

In the Liturgy of Saint James, according to the form in which it is celebrated on the island of Zakynthos, Greece, the anaphora is as follows: