Heaven worship is a Chinese religious belief that predates Taoism and Confucianism, but was later incorporated into both.
The Ancient Chinese believed in a non-corporeal entity called Shangdi, an omnipotent, just, and monotheistic supreme being. Over time, Shangdi became synonymous with Tian, or Heaven. The worship of Heaven is highly ritualistic and requires that the emperor hold official sacrifices and worship at an altar of Heaven, the most famous of which is the Temple of Heaven in Beijing. Idols are not permitted in Heaven worship.
Heaven worship is closely linked with ancestor veneration, as the ancestors are seen as a medium between Heaven and man. The Emperor of China, also known as the Son of Heaven, derived the Mandate of Heaven, and thus his legitimacy as ruler, from his supposed ability to commune with Heaven on behalf of his nation.
Early Abrahamic missionaries saw similarities between Shangdi/Tian and the Abrahamic God, and therefore rendered "God" as "Shangdi" in Chinese. Some Chinese Christian scholars assert that the Christian God and the Chinese Shangdi are in fact the same entity.