In Christianity, a Eucharistic miracle is any miracle involving the Eucharist. In the Roman Catholic, Lutheran, Eastern Orthodox, Methodist, Anglican and Oriental Orthodox Churches, the fact that Christ is really made manifest in the Eucharist is correctly deemed a Eucharistic miracle; however, this is to be distinguished from other manifestations of God. In general, reported Eucharistic miracles usually consist of unexplainable phenomena such as consecrated Hosts visibly transforming into myocardium tissue, being preserved for extremely long stretches of time, surviving being thrown into fire, bleeding, or even sustaining people for decades. Verification of Eucharistic miracles often depends on the religious branch reporting the supposed miracle, but in the case of the Catholic Church, a special task-force or commission investigates supposed Eucharistic miracles before deciding whether they are "worthy of belief." As with other miracles, such as Marian apparitions, belief in approved miracles is not mandated by the Catholic Church, but often serves to reassure believers of God's presence or as the means to "send a message" to the population at large. Anglican Churches have also confirmed extraordinary Eucharistic miracles. It is also not uncommon for religious authorities to allow secular sources to investigate, and verify, at least specifics (such as muscle type) of the supposed miracle.
Roman Catholic Eucharistic Doctrine draws upon a quasi-Aristotelian understanding of reality, in which the core substance or essential reality of a given thing is bound to, but not equivalent with, its sensible realities or accidents. In the celebration of the Eucharist, by means of the consecratory Eucharistic Prayer, the actual substance of the bread and wine are changed into the body and blood of Christ, this change in substance is not, however, the outward appearances of the bread and wine—their accidents—remain as before. This substantial change is called transubstantiation, a term reserved to describe the change itself, the Scholastic philosophical explanation of Christ's presence was defined as a dogma for the Roman Catholic Church by the Council of Trent. In the 13rd session of 11 October 1551, it was promulgated the following conciliar decree: "if anyone says that the substance of bread and wine remains in the Holy Sacrament of the Eucharist together with the Body and Blood of our Lord Jesus Christ and denies that wonderful and extraordinary change of the whole substance of the wine into His blood, while only the species of bread and wine remain, a change which the Catholic Church has most fittingly called transubstantiation, let him be anathema." (Session 13, can.2)".
Protestant views on the fact of Christ's presence in the Eucharist vary significantly from one denomination to another: while many, such as Lutherans, Anglicans, Methodists and the Reformed agree with Roman Catholics that Christ is really present in the Eucharist, they do not accept the definition of transubstantiation to describe it.
According to Thomas Aquinas, in the case of extraordinary Eucharistic Miracles in which the appearance of the accidents are altered, this further alteration is not considered to be transubstantiation, but is a subsequent miracle that takes place for the building up of faith. Nor does the extraordinary manifestation alter or heighten the presence of Christ in the Eucharist, as the miracle does not manifest the physical presence of Christ: "in apparitions of this sort. . . the proper species [actual flesh and blood] of Christ is not seen, but a species formed miraculously either in the eyes of the viewers, or in the sacramental dimensions themselves...."
Some denominations, especially Lutherans, have similar beliefs regarding the Eucharist and the Real Presence, though they reject the Roman Catholic concept of transubstantiation, preferring instead, the doctrine of the sacramental union, in which "the body and blood of Christ are so truly united to the bread and wine of the Holy Communion that the two may be identified. They are at the same time body and blood, bread and wine...in this sacrament the Lutheran Christian receives the very body and blood of Christ precisely for the strengthening of the union of faith." Lutherans hold that the miracle of the Eucharist is effected during the Words of Institution. Both the Eastern Orthodox Churches and the Oriental Orthodox Churches, such as the Coptic Church, insist "on the reality of the change from bread and wine into the body and the blood of Christ at the consecration of the elements," although they have "never attempted to explain the manner of the change," thus rejecting philosophical terms to describe it. The Methodist Church similarly holds that Christ is truly present in the Eucharist "through the elements of bread and wine," but maintains that how He is present is a Holy Mystery. All Anglicans affirm the real presence of Christ in the Eucharist, though Evangelical Anglicans believe that this is a pneumatic presence, while those of an Anglo-Catholic churchmanship believe this is a corporeal presence, but at the same time still rejecting the philosophical explanation of transubstantiation.
Extraordinary Eucharistic miracles
The rarest reported type of Eucharistic miracle is where the Eucharist becomes human flesh as in the miracle of Lanciano which some Catholics believe occurred at Lanciano, Italy, in the 8th century A.D. In fact, Lanciano is only one of the reported cases of Eucharistic miracles where the host has been transformed into human flesh. However, a Eucharistic miracle more commonly reported by Catholics is that of the Bleeding Host, where blood starts to trickle from a consecrated host, the bread consecrated during Mass. Other types of purported miracles include consecrated hosts being preserved for hundreds of years, such as the event of the Miraculous Hosts of Siena. Other miracles include a consecrated host passing through a fire unscathed, stolen consecrated hosts vanishing and turning up in churches, and levitating consecrated hosts.
The Mass at Bolsena, depicted in a famous fresco by Raphael at the Vatican in Rome, was an incident said to have taken place in 1263. A Bohemian priest who doubted the doctrine of transubstantiation, celebrated mass at Bolsena, a town north of Rome. During the mass the bread of the eucharist began to bleed, the blood from the host fell onto the altar linen in the shape of the face of Jesus as traditionally represented, and the priest came to believe. The following year, in 1264, Pope Urban IV instituted the Feast of Corpus Christi to celebrate this miraculous event. A gold-plated silver and enamel reliquary was made in 1337-1338 by Sienese goldsmith Ugolino di Vieri to house the relic, the blood-stained Corporal of Bolsena is still venerated as a major relic in Orvieto Cathedral in central Italy.
There have been numerous other alleged miracles involving consecrated Hosts. Several of these are described below.
A story  from Amsterdam, 1345, claims that a priest was called to administer Viaticum to a dying man. He told the family that if the man threw up, they were to take the contents and throw it in the fire, the man threw up, and the family did what the priest had advised them to do. The next morning, one of the women went to rake the fire and noticed the Host sitting on the grate, unscathed and surrounded by a light, it has apparently passed through both the man's digestive system and the fire unscathed. The story is commemorated with an annual silent procession through central Amsterdam.
According to another story, a farmer in Bavaria took a consecrated Host from Mass to his house, believing that it would give him and his family good fortune, however he was plagued by the feeling that what he had done was very wrong and turned to go back to the church to confess his sin. As he turned, the Host flew from his hand, floated in the air and landed on the ground, he searched for it, but he could not see it. He went back, accompanied by many villagers and the priest, who bent to pick up the Host, having seen it from some distance off, it again flew up into the air, floated, and fell to the ground and disappeared. The Bishop was informed and he came to the site and bent to pick up the Host. Again it flew into the air, remained suspended for an extended time, fell to the ground and disappeared. 
An alleged 1370 Brussels miracle involves an allegation of host desecration; a Jew attempted to stab a communion wafer, but it miraculously bled and was otherwise unharmed. The alleged wafers were venerated in later centuries.
Another claim states that a church in the village of Exilles, Italy, was plundered by a soldier and the monstrance (with the host still inside) was taken, the sack with the monstrance fell off the soldier's donkey and the monstrance fell out. It immediately rose up into the air and was suspended ten feet above the ground, the Bishop was notified and immediately came to view the miracle. When he arrived, the monstrance opened and fell to the ground, leaving the Host still suspended in the air and surrounded by a radiant light.
Caesarius of Heisterbach also recounts various tales of Eucharistic Miracles in his book, Dialogue on Miracles; however, most of the stories he tells are from word of mouth. These stories include Gotteschalk of Volmarstein who saw an infant in the Eucharist, a priest from Wickindisburg who saw the Host turn into raw flesh, and a man from Hemmenrode who saw an image of a crucified Jesus and blood dripping from the Host. All of these images, however, eventually reverted into the Host, he also recounts more extraordinary tales, such as bees creating a shrine to Jesus after a piece of the Eucharist was placed in a beehive, a church that was burnt to ashes while the pyx containing the Eucharist was still intact, and a woman who found the Host transformed into congealed blood after she stored it in a box.
At the 2017 Synodal Mass held at Corpus Christi Anglican Church in Rogers, Rev. Fr. Jason Rice of the Holy Catholic Church Anglican Rite, a Continuing Anglican denomination, affirmed a Eucharistic miracle in which "An image of a heavenly host appeared directly over the chalice immediately after the words of consecration."
- Serratia marcescens#Possible role in medieval miracles - bacteria that can colonize flour/bread/wafer and give it red color, sometimes even resembling blood stains.
- Wandel, Lee Palmer (2006). The Eucharist in the Reformation. Cambridge University Press. p. 260. ISBN 9780521856799.
While Luther had been quite clear that the words of institution themselves, quite autonomous of the minister, effected the miracle of consubstantiation, priests were the medium through which the miracle of transubstantiation occurred.
- Strasburger, Frank C. Why the Anglican Communion Matters. Forward Movement. p. 16.
At the heart of it is the eucharist, the miracle by which the bread and wine become the body and blood of Christ. In that act, individual persons, with all their differences, become one with God and one with another. If that matters, then the Anglican Communion matters.
- Ghose, Tia. "The Science of Miracles: How the Vatican Decides If They're Real". Live Science.
- Rice, Jay (10 June 2017). "Eucharistic Miracle Occurs in Holy Catholic Church Anglican Rite Synodal Mass!". Corpus Christi Holy Catholic Church Anglican Rite. Retrieved 10 June 2017.
- SAUNDERS, WILLIAM. "FR". Catholic Education Research Center. Arlington Catholic Herald. Retrieved 2016-06-22.
- See Edward J. Kilmartin, The Eucharist in the West: History and Theology, ed. Robert J. Daly (Collegeville: Liturgical Press/Pueblo, 1998), 147-153.
- Fr. John A. Hardon, S.J. "Eucharistic Doctrine on the Real Presence".
- Canones Et Decreta Sacrosancti Oecumenici Concilii Tridentini ("Canons and decrees od the Most Holy Ecumenical Council of Trent"). archive.org (in Lithuanian). 1863. p. 54. Archived from the original on Jan 13, 2019.
- "Catechism of the Council of Trent (divulgative version)" (pdf). documentacatholicaomnia.eu (in English, French, and Italian). Archived from the original on Jan 13, 2019.
- See, e.g., Thomas J. Davis, This is My Body: The Presence of Christ in Reformation Thought (Grand Rapids: Baker Academic, 2008).
- Thomas Aquinas, Summa Theologiae III, 76.8 ad 2: "...In huiusmodi apparitionibus. . . non videtur propria species Christi, sed species miraculose formata vel in oculis intuentium, vel etiam in ipsis sacramentalibus dimensionibus...." Translated for Wikipedia.
- Mattox, Mickey L.; Roeber, A. G. (27 February 2012). Changing Churches: An Orthodox, Catholic, and Lutheran Theological Conversation. Wm. B. Eerdmans Publishing. p. 54. ISBN 9780802866943.
In this "sacramental union," Lutherans taught, the body and blood of Christ are so truly united to the bread and wine of the Holy Communion that the two may be identified. They are at the same time body and blood, bread and wine, this divine food is given, more-over, not just for the strengthening of faith, nor only as a sign of our unity in faith, nor merely as an assurance of the forgiveness of sin. Even more, in this sacrament the Lutheran Christian receives the very body and blood of Christ precisely for the strengthening of the union of faith, the "real presence" of Christ in the Holy Sacrament is the means by which the union of faith, effected by God's Word and the sacrament of baptism, is strengthened and maintained. Intimate union with Christ, in other words, leads directly to the most intimate communion in his holy body and blood.
- Harper, Brad; Metzger, Paul Louis (1 March 2009). Exploring Ecclesiology. Brazos Press. p. 312. ISBN 9781587431739.
- Houlden, James Leslie (2003). Jesus in History, Thought, and Culture: An Encyclopedia. ABC-CLIO. p. 185. ISBN 9781576078563.
The Copts are fearful of using philosophical terms concerning the real presence of Christ in the Eucharist, preferring uncritical appeals to biblical passages like 1 Cor. 10.16; 11.23-29 or the discourse in John 6.26-58.
- Neal, Gregory S. (19 December 2014). Sacramental Theology and the Christian Life. WestBow Press. p. 111. ISBN 9781490860077.
For Anglicans and Methodists the reality of the presence of Jesus as received through the sacramental elements is not in question. Real presence is simply accepted as being true, its mysterious nature being affirmed and even lauded in official statements like This Holy Mystery: A United Methodist Understanding of Holy Communion.
- Abraham, William J.; Watson, David F. (1 March 2013). Key United Methodist Beliefs. Abingdon Press. p. 1. ISBN 9781426771224.
Charles Wesley wrote a marvelous collection of hymns that offer an amazing vision of Christ's mysterious, yet real, presence in the bread and the wine.
- Poulson, Christine (1999). The Quest for the Grail: Arthurian Legend in British Art, 1840-1920. Manchester University Press. p. 40. ISBN 9780719055379.
By the late 1840s Anglo-Catholic interest in the revival of ritual had given new life to doctrinal debate over the nature of the Eucharist. Initially, 'the Tractarians were concerned only to exalt the importance of the sacrament and did not engage in doctrinal speculation'. Indeed they were generally hostile to the doctrine of transubstantiation, for an orthodox Anglo-Catholic such as Dyce the doctrine of the Real Presence was acceptable, but that of transubstantiation was not.
- Spurr, Barry (3 April 2010). Anglo-Catholic in Religion. Lutterworth Press. p. 100. ISBN 0718830733.
The doctrine had been affirmed by Anglican theologians, through the ages, including Lancelot Andrewes, Jeremy Taylor (who taught the doctrine of the Real Presence at the eucharist, but attacked Roman transubstantiation), William Laud and John Cosin - all in the seventeenth century - as well as in the nineteenth century Tractarians and their successors.
- Linoli O. "Histological, immunological and biochemical studies on the flesh and blood of the eucharistic miracle of Lanciano (8th century)." Quad Sclavo Diagn. 1971 Sep; 7(3):661-74
- Levy, Ian; Macy, Gary; Ausdall, Kristen Van (2011-10-28). A Companion to the Eucharist in the Middle Ages. BRILL. pp. 584–585. ISBN 9004201416.
- Dutch-language description: "In Amsterdam, gelegen binnen het bisdom Utrecht, was een man zwaar ziek en vreesde te sterven. Om hem de laatste sacramenten toe te dienen werd een priester geroepen. Deze gaf hem na de biecht het heilig sacrament van de eucharistie. Echter, na het eten van de geconsacreerde hostie kon de zieke een braakneiging niet onderdrukken. Hij ging naar de brandende haard van zijn kamer en braakte het sacrament daarin uit. Daarop bleek dat de zieke niet alleen de hostie onbeschadigd had uitgebraakt, maar dat bovendien het brood niet door het hoogopvlammende vuur werd aangetast."
- "Erding, Germany: Eucharistic Miracle in the Church of the Holy Blood". The Catholic Travel Guide. Retrieved 2018-12-31.
- Commission Nationale Catholique pour les Relations avec le Monde Juif. "Le Miracle du St Sacrament" (in French). Brussels Cathedral. Archived from the original on 5 April 2011. Retrieved 8 April 2014.
- Dialogue on Miracles, by Caesarius of Heisterbach, London : G. Routledge & sons, ltd., 1929
- Eucharistic Miracles, by Joan Carroll Cruz, OCDS, TAN Books and Publishers, Inc., 1987. ISBN 978-0-89555-303-4
- Sammaciccia, Bruno (1977): "Il miracolo eucaristico di Lanciano". A French translation of this paper is available at http://www.christ-roi.net/index.php/Le_miracle_eucharistique_de_Lanciano_(Bruno_Sammaciccia), retrieved on December 15, 2008.
- The Real Presence Association - Eucharistic Miracles
- Eucharistic Miracles
- http://www.zenit.org/english/visualizza.phtml?sid=70440[permanent dead link]
- https://web.archive.org/web/20110102131821/http://www.zenit.org/article-12933?l=english (Lanciano, and Congress about such miracles)