Tritheism is the belief that there are three equally powerful gods who form a trinity. The gods are envisaged as having separate powers or spheres of influence but working together. In this respect Tritheism differs from Dualism, which typically envisages two opposed Divine powers in conflict with one another.

Unitarians and other nontrinitarians claim the orthodox trinitarian Christian doctrine of the Holy Trinity of Father, Son and Holy Ghost is in fact Tritheism, since these distinct "personalities" seem to act independently of one another, though not in conflict.

Proponents of trinitarianism claim that the three persons of the Trinity do not have separate powers, since they are omnipotent, and do not have separate spheres of influence, since their sphere of influence is unlimited. They argue that the persons of the Trinity have one divine essence and are indivisible, whereas Tritheism appears to suggest three separate gods. The (unknown) author of the Athanasian Creed attempted to distinguish Trinitarianism from both Tritheism and Modalism.

At various times in the history of Christianity, various theologians were accused by the church of tritheism, which the church treated as heresy. John Philoponus , an Aristotelian and monophysite in Alexandria about the middle of the sixth century, was charged with tritheism because he saw in the Trinity three natures, substances, and deities, according to the number of persons. He sought to justify this view by the Aristotelian categories of genus, species, and individuum.

Tritheism was revived in the Anglican Church in 1690 by Dean Sherlock in his work, "Vindication of the Doctrine of the Holy and ever Blessed Trinity." He maintained that, with the exception of a mutual consciousness of each other, which no created spirits can have, the three divine persons are "three distinct infinite minds" or "three intelligent beings." He was widely opposed by trinitarians. More recently Mormonism, with its very different conception of the Trinity is sometimes characterised by other Christian denominations as tritheistic.

The so-called Hindu Trinity of Brahma the creator, Vishnu the preserver and Shiva the destroyer has also been said to constitute a Tritheistic belief system. Like the Chistian Trinity, these beings are understood to work ultimately in harmony with one another. However, this Hindu trinity does not have doctrinal status as in trinitarian Christianity, but is posited as simply one of many ways in which the Divine order of the universe may be understood.