Monotheism is defined by the Encyclopædia Britannica as belief in the existence of one god or in the oneness of God. The Oxford Dictionary of the Christian Church gives a more restricted definition: "belief in one personal and transcendent God", as opposed to polytheism and pantheism. A distinction may be made between exclusive monotheism, exemplified by Judaism, Christianity and Islam, and both inclusive monotheism and pluriform monotheism which, while recognising many distinct gods, postulate some underlying unity. In this broader sense of the word, monotheistic religions include Atenism, the Bahá'í Faith, Cao Dai, Cheondoism (Cheondogyo), Deism, Eckankar, Hinduism (Vaishnavism, Shivaism), Ravidassia, Seicho no Ie, Sikhism, Tenrikyo and Zoroastrianism.
Vishnu (Sanskrit: विष्णु) is the Vedic Supreme God (including his different avatars) in Hinduism, and is venerated as the Supreme Being in Vaishnavism. Vishnu is also known as Narayana and Hari (See Keshava Namas) and is venerated as Purushottama or Supreme Purusha in ancient sacred texts like the Bhagavad Gita, the Vedas and the Puranas. He is the Supreme Purusha of Purusha Sukta. The Vishnu Sahasranama, (the thousand names of Vishnu) of the Mahabharata declares Vishnu as Paramatman (supreme soul) and Parameshwara (supreme God). It describes Vishnu as the all-pervading essence of all beings, the master of—and beyond—the past, present and future, the creator and destroyer of all existences, one who supports, sustains and governs the universe and originates and develops all elements within.
Vaishnavism sees Vishnu as the Supreme God, and venerates him as the Supreme Being. Smarta followers of Adi Shankara, among others, venerate Vishnu as just one of the five primary forms of God, namely Shiva, Vishnu, Devi, Surya and Ganesha; who are all seen as equal reflections of the one Brahman, rather than as distinct beings. His supreme status is declared in Hindu sacred texts; the Vedas, the Bhagavad Gita, the Bhagavata Purana and other Sattva Puranas which all declare Vishnu as Supreme God. Vishnu incarnates on Earth from time to time, as an avatar, to eradicate evil forces, to restore the dharma and to liberate the worthy ones or devotees from the cycle of births and deaths.