A sacred sound and a spiritual icon in Dharmic religions. A mantra in Hinduism, Buddhism and Jainism. Om is a spiritual symbol (pratima) referring to Atman (soul, self within) and Brahman (ultimate reality, entirety of the universe, truth, divine, supreme spirit, cosmic principles, knowledge).

Om is part of the iconography found in ancient and medieval era temples and monasteries.

Some scholars consider Om to have been variously held as the "cosmic sound" or "mystical syllable" in ancient India, or simply as "affirmation to something divine", or as symbolism for abstract spiritual concepts in the Upanishads. The syllable "Om" is described with various meanings in the Vedas and different early Upanishads. The meanings include "the sacred sound, the Yes!, the Vedas, the Udgitha (song of the universe), the infinite, the all encompassing, the whole world, the truth, the ultimate reality, the finest essence, the cause of the Universe, the essence of life, the Brahman, the Atman, the vehicle of deepest knowledge, and Self-knowledge.