In Tenrikyo, God is a single divine being and creator of the entire universe. God in Tenrikyo is most commonly referred to as Oyagami (親神) (lit. 'God the Parent'), Tenri-Ō-no-Mikoto (天理王命) (lit. 'absolute ruler of divine reason'), and Tsukihi (月日) (lit. 'Moon-Sun').

The first two characters in the Japanese kanji for Tenri-Ō-no-Mikoto are 天理, where 天 refers to heaven or divinity, and 理 refers to reason or knowledge, thus "Tenri" (天理) refers to divine or heavenly knowledge, and in a sense adds a divine nature to truth itself whereas "天理" also means "natural law" or its pseudonym, "divine law." The English name most frequently used to refer to Tenri-Ō-no-Mikoto outside of ritual is "God the Parent"; in Japanese, the equivalent common names are Oyagami (親神) and Oyagami-sama (親神様). In Tenrikyo, God has no gender.

Tenrikyo followers vary in their understanding of this creator, from the early understanding of spirit (kami, god/deity) through the underlying natural causality (Tsukihi, moon-sun) and eventually to an understanding of a parental relationship between the creator and themselves (oya, parent). This progression of understanding is a key teaching of Tenrikyo, where it is accepted that everything must proceed "step by step" — by small stages of understanding instead of by great leaps of faith.

In historical documents and scriptures related to Tenrikyo, a number of different appellations are ascribed to God. The most commonly used names for God are:

In the Ofudesaki, God identified as three different entities. In 1869, when the first verses were composed, God initially identified as kami (神), a spirit in the Japanese Shinto tradition. The designation kami was broader than the Abrahamic notion of God, as it could be applied to any object that possessed divine power or inspired awe, such as animals, trees, places, and people. However, the Ofudesaki stressed the uniqueness of the kami (神) by adding various qualifiers such as moto no kami (元の神; God of origin), shinjitsu no kami (真実の神; God in truth), and kono yō o hajimeta kami (このよふをはじめた神; God who began this world). From 1874, God began to identify as tsukihi (月日), or moon-sun, and from 1879, God began to identify as oya (をや), or parent, though kami and tsukihi continued to be used until the last part of the scripture.

In Tenrikyo's creation story, outlined in the Ofudesaki and elaborated upon in various notes on her talks known collectively as kōki, there are ten figures credited with the creation of human beings. Some Tenrikyo authorities suggest that two of these figures, Kunitokotachi-no-Mikoto and Omotari-no-Mikoto, represent tsukihi, or more precisely the duality tsuki-sama (月様) and hi-sama (日様). The other eight figures are tools subordinate to tsukihi that were drawn in, consulted, and trained in the creation of human beings.

In the Mikagura-uta, the songs of Tenrikyo's liturgy, God is commonly referred to as kami. At the end of most of the songs, God is invoked with the name Tenri-Ō-no-Mikoto (てんりおうのみこと or 天理王命), or "absolute ruler of divine reason."

The historical sources written during Nakayama Miki's lifetime and in the years following her death suggest a number of other appellations of God. In Nakayama Shinnosuke's Oyasama gyōden, the source on which The Life of Oyasama is primarily based, Miki refers to God as ten no shōgun (天の将軍, Shōgun of Heaven) in the initial revelation. In early attempts to obtain religious sanctions from the Yoshida Administrative Office of Shinto and a Shingon Buddhist temple, the name of God was recorded as Tenrin-Ō-Myōjin (天輪王明神) and Tenrin-Ō-Kōsha (転輪王講社) respectively. An early doctrine of the Tenrikyo church, written to conform to the State Shinto doctrine at the time, records the name as Tenri-Ōkami.