Zhengyi Dao, also known as the Way of Orthodox Unity, Teaching of the Orthodox Unity, and Branch of the Orthodox Unity is a Chinese Taoist movement that traditionally refers to the same Taoist lineage as the Way of the Five Pecks of Rice and Way of the Celestial Masters, but in the period of the Tang dynasty and its history thereafter. Like the Way of Celestial Masters, the leader of Zhengyi Taoism was known as the Celestial Master.

Taoism or Daoism is a diverse tradition indigenous to China, variously characterized as both a philosophy and a religion. Taoism emphasizes living in harmony with the Tao—generally understood as being the impersonal, enigmatic process of transformation ultimately underlying reality. The concept originates in the Chinese word 道, which has numerous related meanings: possible English translations include 'way', 'road', and 'technique'. Taoist thought has informed the development of various practices within the Taoist tradition and beyond, including forms of meditation, astrology, qigong, feng shui, and internal alchemy. A common goal of Taoist practice is self-cultivation resulting in a deeper appreciation of the Tao, and thus a more harmonious existence. There are different formulations of Taoist ethics, but there is generally emphasis on virtues such as effortless action, naturalness or spontaneity, simplicity, and the three treasures of compassion, frugality, and humility. Many Taoist terms lack simple definitions and have been translated in several different ways.