Perichoresis (or Circuminsession or Interpenetration) is a term in Christian theology first found within the Church Fathers but now reinvigorated among contemporary figures such as C. Baxter Kruger, Jurgen Moltmann, Miroslav Volf and John Zizioulas, amongst others. The term first appears in Gregory of Nazianzus but was explored more fully in the work of John of Damascus. It refers to the mutual inter-penetration and indwelling within the threefold nature of the Trinity, God the Father, the Son and the Holy Spirit.

Although clear references to full-blown Trinitarian theology in the New Testament are rare, it can be seen between two persons of the Trinity in passages such as the following from John's Gospel:"the Father is in the Son, and the Son in the Father."

The relationship of the Triune God is intensified by the relationship of perichoresis. This indwelling expresses and realizes fellowship between the Father and the Son. It is intimacy. Jesus compares the oneness of this indwelling to the oneness of the fellowship of his church from this indwelling. "That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us (John 17:21)."