Communion under both kinds in Catholicism is the reception under both "species" (i.e., both the consecrated bread and wine) of the Eucharist. Denominations of Christianity that hold to a doctrine of Communion under both kinds may believe that a Eucharist which does not include both bread and wine as elements of the religious ceremony is not valid, while others may consider the presence of both bread and wine as preferable, but not necessary, for the ceremony. In some traditions, the second element may be grape juice in place of wine containing alcohol.

In reference to the Eucharist as a sacrifice, Communion under both kinds belongs at least to the integrity and essence, of the rite, and may not be omitted without violating the precept of Christ: "Do this in remembrance of me" (Luke 22:19). This is mentioned implicitly by the Council of Trent (Sess. XXI, c. i; XXII, c. i), and the Second Vatican Council emphasised that "the dogmatic principles which were laid down by the Council of Trent [remain] intact". The General Instruction of the Roman Missal states that the people "should share the cup when it is permitted. Then, Communion is a clearer sign of sharing in the sacrifice that is actually being celebrated."

Catholicism teaches that Christ is sacramentally (and equally) present under each species, and therefore if a person receives only one species, Christ is fully present and nothing is lacking.

In the Early Church, Communion was ordinarily administered and received under both kinds. That such was the practice is mentioned by Paul in I Corinthians 11:28. But side by side in the Early Church there existed the custom of communicating in certain cases under one kind alone: for example, when people took home some of the Eucharist after Sunday worship and communicated during the week, or when the Eucharist was brought to the sick.

By the Middle Ages, the Church had become, like most of European society, increasingly hierarchical. There was much stress on being holy when receiving Communion, and a greatly heightened appreciation of the holiness of the sacramental elements (bread and wine). This meant that all who approached the altar were to be as pure as possible, and inevitably led to the exclusion of the laity from receiving the Eucharist under both kinds, reserving the practice to the clergy. It is difficult to say when the practice of offering the chalice to the people stopped, but it seems to have been part of the way in which Church authorities sought to prevent anything disrespectful happening to the Eucharist; it was also, by this time, that the host (the Communion bread) was given only on the tongue.^{[citation needed]} It is generally thought by historians^[who?] that the practice of offering Communion to the laity under one species alone began during the 12th or 13th century, and had become a common Church practice by the 14th century.

This practice was challenged by the Bohemian reformer, Jacob of Mies, who in 1414 began to offer Communion under both kinds to his congregation in the Church of St. Martin in the Wall. The matter was reviewed by the 13th Session of the Council of Constance, in 1415; the council rejected the grounds for offering the chalice to lay people and banned the practice. This became the most emblematic issue of the Hussite Wars, which resulted in the permission of the communion under both kinds for Utraquists in Bohemia in 1433 (it would be banned again in 1627 and allowed again by the Patent of Toleration in 1781). In the following century, this was challenged again by the Protestant Reformers, including Martin Luther, John Calvin and Huldrych Zwingli. The Council of Trent referred to the pope the question whether the petition of the Holy Roman Emperor to have the use of the chalice allowed in his dominions be granted; in 1564 Pius IV did grant this permission to some German bishops, provided certain conditions were fulfilled. However, his concession was withdrawn in the following year. The practice, by then, does not seem to have been well received among Catholic faithful; the practice of giving communion under both kinds was, by many, already regarded as a 'Protestant' practice.

In the 20th century, Catholic liturgical reformers began to press for a return to Communion under both kinds, citing the practice of the Church before the 13th century. There were spirited debates over the issue at the Second Vatican Council, resulting in a compromise. The following text was finally issued by the bishops; "communion under both kinds may be granted when the bishops think fit, not only to clerics and religious, but also to the laity, in cases to be determined by the Apostolic See, as for instance, to the newly ordained in the Mass of their sacred ordination, to the newly professed in the Mass of their religious profession, and to the newly baptized in the Mass which follows their baptism". Regular use of Communion under both kinds requires the permission of the bishop, but bishops in many countries have given blanket authorisation to administer Holy Communion in this way. In the United States, the Notre Dame Study of Catholic Parish Life showed that by 1989, slightly less than half of the parishes in its survey offered the chalice to their congregations. As a result of the 2020–2022 pandemic, the practice of giving Communion under both kinds seems to have been, once again, restrained.

(Also applicable to the appropriate Eastern Catholic Churches.)