Mūla Bandha is a primary Bandha (a lock) in traditional yoga. The earliest textual mention of mūla bandha is in the 12th century Shaiva Natha text Gorakṣaśataka which defines it as a yogic technique to achieve mastery of breath and to awaken the goddess Kuṇḍalinī.
Mula Bandha (Sanskrit: मूल बंध) is from Mūla, meaning variously root, base, beginning, foundation, origin or cause; and Bandha meaning bond, fetter, or "catching hold of". Gorakṣhaśataka defines mūla bandha as:
[The yogi] forces the downward-moving apāna breath to move upwards by means of contraction. Yogis call this mūla bandha, "the root lock." When apāna has turned upwards and reached the orb of fire, then the flame, fanned by the wind, rises high. As a result, fire and apāna reach prāṇa, which is hot by nature. The overheated prāṇa creates a blaze in the body, which heats the sleeping Kuṇḍalinī and wakes her up. Like a snake struck by a stick, she hisses and straightens herself. As if entering a snake-hole, she enters the Brahmā naḍi. Therefore, yogis should maintain the regular practice of mūla bandha. Gorakṣaśataka
Iyengar defines Mūla Bandha as "A posture where the body from the anus to the navel is contracted and lifted up and towards the spine. This is qualified in that the actual muscle contracted is not the sphincter muscle nor the muscle which cessates urination, but the muscle equidistant between the two.
Maehle defines it as "root lock" and further specifies that:
The root referred to here is the root of the spine, the pelvic floor or, more precisely, the centre of the pelvic floor, the perineum. The perineum is the muscular body between the anus and the genitals. By slightly contracting the pubo-coccygeal (PC) muscle, which goes from the pubic bone to the tail bone (coccyx), we create an energetic seal that locks prana into the body and so prevents it from leaking out at the base of the spine. Mula Bandha is said to move prana into the central channel, called sushumna, which is the subtle equivalent of the spine.— 
Mūla Bandha is a primary Bandha in traditional yoga. Iyengar likens the functionality of the Bandha and especially Mūla Bandha to "safety-valves which should be kept shut during the practice of kumbhakas". He specifies the energetic prāṇas of Vāyus engaged through Mūla Bandha as: "...Apāna Vāyu (the prāṇa in the lower abdomen), whose course is downwards, is made to flow up to unite with Prāna Vāyu, which has its seat within the region of the chest." He cautions that "Mūla Bandha should be attempted first in antara kumbhaka (retention after inhalation). The region of the lower abdomen between the navel and the anus is contracted towards the spine and pulled up to the diaphragm. He further states that "While practicing Mūla Bandha, the yogi attempts to reach the true source or mūla of creation."
- Mallinson 2012, p.261
- Iyengar, 1976: p.515
- Iyengar, 1976: p.459
- Iyengar, 1976: pp.435–437
- Iyengar, 1976: p.525
- Mallinson 2012, p. 269.
- Iyengar, 1976: p.525
- Maehle, Gregor (2007). Ashtanga Yoga: Practice and Philosophy (Paperback). New World Library. ISBN 1-57731-606-1 & ISBN 978-1-57731-606-0, p.11
- Iyengar, 1976: p.435
- Iyengar, B. K. S. (1966, 1976). Light on Yoga, Thorsons.ISBN 1-85538-166-4
- Maehle, Gregor (2007). Ashtanga Yoga: Practice and Philosophy, New World Library. ISBN 1-57731-606-1 & ISBN 978-1-57731-606-0
- Mallinson, James; Singleton, Mark (2017). Roots of Yoga. Penguin Books. ISBN 978-0-241-25304-5. OCLC 928480104.
- Singleton, Mark (2010). Yoga Body : the origins of modern posture practice. Oxford University Press. ISBN 978-0-19-539534-1. OCLC 318191988.
- Mallinson, James (2012). "The Original Gorakṣaśataka". In White, David Gordon (ed.). Yoga in Practice. Princeton University Press. ISBN 978-0691140858.