Cao Đài (Vietnamese: [kāw ɗâj] ( listen), also Caodaiism) is a syncretistic, monotheistic religion, officially established in the city of Tây Ninh, southern Vietnam in 1926. Đạo Cao Đài is the religion's shortened name; its full name is Đại Đạo Tam Kỳ Phổ Độ (Great Religion [of The] Third Period [of] Revelation [and] Salvation).

Cao means "high" and Đài means "dais" (as in a platform or altar raised above the surrounding level to give prominence to the person on it). Figuratively, it means that highest spiritual place where God reigns. Caodaiists often use the term Đức Cao Đài (Venerable Cao Đài) as the abbreviated name for God, the creator of the universe, whose full title is Cao Đài Tiên Ông Đại Bồ Tát Ma-ha-tát (translation: Cao Đài [the] Ancient Sage [and] Great Bodhisattva Mahasattva). According to Caodaiists, the full title was purposefully chosen by God because within it are representations of the Three Teachings: Snt, Sage and Buddha. Caodaiists credit God as the religion's founder. They believe the teachings, symbolism and organization were communicated directly from God. Even the construction of the Tây Ninh Holy See is claimed to have had divine guidance. Cao Đài's first disciples, Ngô Văn Chiêu, Cao Quỳnh Cư, Phạm Công Tắc and Cao Hoài Sang, claimed to have received direct communications from God, who gave them explicit instructions for establishing a new religion that would commence the Third Era of Religious Amnesty.

Cao or CaO may refer to:

Dai can mean: