Tenri-Ō-no-Mikoto (天理王命) is the name of the single God and creator of the entire universe in Tenrikyo belief. 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 name is Oyagamisama. 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.
History
In 1880, in order to evade continuous persecution by the government, Tenrikyo placed itself under the administration of a Shugendo temple named Jifukuji. During this time Tenri-Ō-no-Mikoto was officially called Tenrin-Ō-Nyorai and the kanji of various other deities were changed, but by 1890 Tenrikyo was given approval by the Meiji government and the original names were restored.