In Christianity, Sabellianism (also known as modalism) is the third-century belief that the three persons of the Trinity are merely different modes or aspects of God, rather than three distinct persons. It is attributed to Sabellius, who taught a form of this doctrine in Rome in the third century. Hippolytus knew Sabellius personally and mentioned him in the Philosophumena. He knew Sabellius disliked Trinitarian theology, yet he called Modal Monarchism the heresy of Noetos, not that of Sabellius. Sabellianism was embraced by Christians in Cyrenaica, to whom Demetrius, Patriarch of Alexandria, wrote letters arguing against this belief.

The chief opponent of Sabellianism was Tertullian, who labelled the movement "Patripassianism", from the Latin words patris for "father", and passus for "to suffer" because it implied that the Father suffered on the Cross. It was Coined by Tertullian in his work Adversus Praxeas, Chapter

Today, Sabellianism is rejected by most types of Christianity. It is accepted primarily by some Pentecostal groups, sometimes referred to as Oneness Pentecostals or "Jesus Only" Pentecostals.

Historic Sabellianism taught that God the Father was the only person of the Godhead. This teaching proports that the identity of God the Father and Jesus is the same. According to this belief, the terms "Father" and "Holy Spirit" both describe the one God who dwelt in Jesus. Some Oneness detractors call this the "Jesus-Only doctrine". Sabelianismo