Yoga is a group of ancient spiritual practices originating in India. As a general term in Hinduism it has been defined as referring to "technologies or disciplines of asceticism and meditation which are thought to lead to spiritual experience and profound understanding or insight into the nature of existence." Yoga is also intimately connected to the religious beliefs and practices of the other Indian religions.

Outside India, Yoga is mostly associated with the practice of asanas (postures) of Hatha Yoga or as a form of exercise, although it has influenced the entire Indian religions family and other spiritual practices throughout the world.

Hindu texts discussing different aspects of yoga include the Upanishads, the Bhagavad Gita, the Yoga Sutras of Patanjali, the Hatha Yoga Pradipika, the Shiva Samhita, and many others.

Major branches of Yoga include: Hatha Yoga, Karma Yoga, Jnana Yoga, Bhakti Yoga, and Raja Yoga. Raja Yoga, known simply as Yoga in the context of Hindu philosophy, is one of the six orthodox (āstika) schools of thought, established by the Yoga Sutras of Patanjali.

In Indian philosophy, Yoga is the name of one of the six orthodox philosophical schools. The Yoga philosophical system is closely allied with the Samkhya school. The Yoga school as expounded by Patanjali accepts the Samkhya psychology and metaphysics, but is more theistic than the Samkhya, as evidenced by the addition of a divine entity to the Samkhya's twenty-five elements of reality. The parallels between Yoga and Samkhya were so close that Max Müller says that "the two philosophies were in popular parlance distinguished from each other as Samkhya with and Samkhya without a Lord...." The intimate relationship between Samkhya and Yoga is explained by Heinrich Zimmer: