Abstract: The nature of the Trinity is a central and salvific doctrine within biblical Christianity. The divine nature of the person of God the Father, Son and Holy Spirit is pertinent to Christian teachings and a proper understanding of God is crucial to authentic worship and belief. Cults or heterodoxic religions, such as Mormonism, Jehovah's Witnesses, and Oneness Pentecostalism have discounted, distorted or dismissed the Three-in-One doctrine of the Trinity, as found in classical Christian theism. These false doctrines can affect teachings about justification, sanctification, the role and work of the cross and an understanding of the nature of God. The nature of the Trinity can be better understood after a careful examination of three major cultic offshoots of Christianity and their distortion of the Trinity, as evidenced by their teachings in comparison to Scripture.