Om (or Aum) (listen ; Sanskrit: ॐ, ओम्, romanized: Ōṃ) is a sacred sound, syllable, mantra, and an invocation in Hinduism. Om is one of the most important symbols of Hinduism. It is variously said to be the essence of the supreme Absolute, consciousness, Ātman, Brahman, or the cosmic world. In Indic traditions, Om serves as a sonic representation of the divine, a standard of Vedic authority and a central aspect of soteriological doctrines and practices. The syllable is often found at the beginning and the end of chapters in the Vedas, the Upanishads, and other Hindu texts.

Om emerged in the Vedic corpus and is said to be an encapsulated form of Samavedic chants or songs. It is a sacred spiritual incantation made before and during the recitation of spiritual texts, during puja and private prayers, in ceremonies of rites of passage (samskara) such as weddings, and during meditative and spiritual activities such as Pranava yoga. It is part of the iconography found in ancient and medieval era manuscripts, temples, monasteries, and spiritual retreats in Hinduism, Buddhism, Jainism, and Sikhism. As a syllable, it is often chanted either independently or before a spiritual recitation and during meditation in Hinduism, Buddhism, and Jainism.

The syllable Om is also referred to as Onkara (Omkara) and Pranava among many other names.