Tian (Chinese: 天, Tiān, T'ien, "sky, heavens") is one of the oldest Chinese terms for the cosmos and a key concept in Chinese mythology, philosophy, and religion. During the Shang Dynasty (17–11th centuries BCE), the Chinese called their supreme god Shangdi (上帝, "Lord on High") or Di ("Lord"); during the Zhou Dynasty, Tian became synonymous with this figure. Heaven worship was, before the 20th century, an orthodox state religion of China.
In Taoism and Confucianism, Tian is often translated as "Heaven" and is mentioned in relationship to its complementary aspect of Dì (地), which is most often translated as "Earth". These two aspects of Taoist cosmology are representative of the dualistic nature of Taoism. They are thought to maintain the two poles of the Three Realms (三界) of reality, with the middle realm occupied by Humanity (人, Ren).