The holy kiss is an ancient traditional Christian greeting, also called the kiss of peace or kiss of charity, and sometimes the "brother kiss" (among men), or the "sister kiss" (among women). Such greetings signify a wish and blessing that peace be with the recipient, and besides their spontaneous uses they have certain ritualized or formalized uses long established in Christian liturgy.

In the New Testament of the Christian Bible, the injunction for believers to greet one another with a holy kiss is given in five places in the New Testament. The early Christian apologist Tertullian wrote that before leaving a house, Christians are to give the holy kiss and say "peace to this house". Apostolic Constitutions likewise declared "Then let the men apart, and the women apart, salute each other with a kiss in the Lord."

Among Conservative Anabaptists, such as the Conservative Mennonite churches and the Dunkard Brethren Church, the holy kiss is counted as an ordinance of the Church. As such, denominations of Conservative Anabaptism observe the practice of the holy kiss. Other denominations (such as the Catholic Church and Lutheran Churches) use various forms of greeting to serve equivalent purposes; these include kisses, handshakes, gestures or hugs, any of which may be called a sign of peace.

It was the widespread custom in the ancient eastern Mediterranean for men to greet each other with a kiss. It was also the custom in ancient Judea and practiced also by Christians. However, the New Testament's references to a holy kiss (Ancient Greek: ἐν ἁγίω φιλήματι, en hagio philemati) and kiss of love (ἐν φιλήματι ἀγάπης) transformed the character of the act beyond a greeting; furthermore, in the early Church, "the verbal exchange of 'peace' with a kiss appears to be a Christian innovation, there being no clear example in pre-Christian literature." The holy kiss was thus followed as a biblical teaching, rather than a cultural tradition. Such a kiss is mentioned five times in the concluding section of letters in the New Testament:

The early Christian apologist Tertullian wrote that before leaving a house, Christians are to give the holy kiss and say "peace to this house". Justin Martyr, Origen, and Cyprian attested to the practice of the holy kiss among Christians as well.

Though also practiced outside of church, since the aforementioned epistles were addressed to Christian communities, the practice of the holy kiss was especially relevant in communal worship. It has been noted that these mentions of the holy kiss come at the end of these epistles, indicating "that the kiss was shared in conjunction with the benedictions at the conclusion of worship services" though it soon "became associated with the Eucharist" and thus "its location during the worship service moved forward in time to the celebration of Communion." The holy kiss was seen as an essential part of preparing to partake in the Eucharist:

Peace, reconciliation, and unity were the very essence of the church's life; without them communion would have been a sham. Bestowed by the Spirit and experienced in prayer, their liturgical expression—which pointed forward to the eucharist—was the holy kiss.

For the early Christians, the holy kiss "was associated with the peace and unity given by the Holy Spirit to the congregation."