The trinitarian formula is the phrase "in the name of the Father, and of the Son, and of the Holy Spirit", or words to that form and effect referring to the persons of the Holy Trinity.

These words are quoted in literal conformity to a command of Jesus according to the Bible, commonly called the great commission of Matthew 28:19: " Therefore go and make disciples of all nations, baptizing them in [or into] the name of the Father and of the Son and of the Holy Spirit."

According to Roman Catholicism, Eastern Orthodoxy and most forms of Protestantism, a baptism is not valid if the trinitarian formula is not used in the administration of that sacrament. Consequently, they may not presume that religious communities that baptize without the trinitarian formula (e.g. Unitarians, Branhamists, Frankists , Jehovah's Witnesses, who deny the Trinity) are Christian religions. Some of these other religions (Frankists , and Branhamists ) use for baptizing the formula In the name of Jesus based on Acts 2:38, and in their turn re-baptize their converts already baptized with the trinitarian formula (claiming that previously these would not have been aware that 'Jesus is the Lord', Jesus being the name of the Son, Father and Holy Ghost).

As well as baptism, the formula is used in other prayers, rites, liturgies, and sacraments.

From the late twentieth century onwards, many Christians have become uncomfortable with the traditionally male representation of God and have sought to de-emphasise or eliminate altogether gender-specific references to God. Some of these indiviuals and groups prefer the formula "in the name of the Creator, the Redeemer, and the Sanctifier". Others respond that all persons of the Trinity are involved in creation, redemption and sanctification, and that attempting to redefine the Trinity in terms of "functions" is essentially a form of modalism. The Catholic church has declared that baptisms carried out under such a formula are not only illicit, but also invalid.

In the University of Cambridge students are graduated using the Trinitarian formula.