The Christian doctrine of the Trinity defines God as three divine persons (Greek: ὑποστάσεις): the Father, the Son (Jesus Christ), and the Holy Spirit. The three persons are distinct yet coexist in unity, and are co-equal, co-eternal and consubstantial (Greek: ὁμοούσιοι). Put another way, the three persons of the Trinity are of one being (Greek: οὐσία). The Trinity is considered to be a mystery of Christian faith.

According to this doctrine, there is only one God in three persons. Each person is God, whole and entire. They are distinct from one another in their relations of origin: as the Fourth Lateran Council declared, "it is the Father who generates, the Son who is begotten, and the Holy Spirit who proceeds". While distinct in their relations with one another, they are one in all else. The whole work of creation and grace is a single operation common to all three divine persons, who at the same time operate according to their unique properties, so that all things are from the Father, through the Son and in the Holy Spirit.