Three outer classes of tantra

The three outer or lower classes of tantra (Wyl. rgyud sde 'og ma sum, phyi'i rgyud) are classes of tantra which are common to both the Nyingma and Sarma schools of Tibetan Buddhism. They are also called the three tantras of vedic asceticism. They are:

• the kriya tantra,
• the charya tantra and
• the yoga tantra.