The Muktika canon of 108 Upanishads is headed by 10 Mukhya Upanishads. These are the ten oldest Upanishads, known to and commented upon by the 9th century scholar Shankara. Sanskrit mukhya means "principal", "chief", or "eminent". The ten Mukhya Upanishads probably all predate the Common Era, and they are accepted as shruti by all Hindus. They are listed with their associated Veda (ṚV, SV, ŚYV, KYV, AV):

1. Īṣa, (ŚYV) "The Inner Ruler"
2. Kena (SV) "Who moves the world?"
3. Kaṭha (KYV) "Death as Teacher"
4. Praṣna, (AV) "The Breath of Life"
5. Muṇḍaka (AV) "Two
   
   
   
   modes of Knowing"
6. Māṇḍūkya (AV) "Consciousness and its phases"
7. Taittirīya (KYV) "From Food to Joy"
8. Aitareya, (ṚV) "The Microcosm of Man"
9. Chāndogya (SV) "Song and Sacrifice"
10. Bṛhadāraṇyaka (ŚYV)

Linguistically, the oldest of these (Bṛhadāraṇyaka, Chāndogya) belong to the "Brahmana" period of Vedic Sanskrit, predating Panini. A middle layer (Kaṭha) belongs to the "Sutra" period of late Vedic Sanskrit, roughly contemporary with Panini, and the youngest are in early Classical Sanskrit, approximately contemporary with the Bhagavad Gita (roughly from the 4th century BC to the beginning of the Common Era).

See also

• Samanya Vedanta Upanishads