Mukhya Upanishads, also known as Principal Upanishads, are the most ancient and widely studied Upanishads of Hinduism. Composed between 800 BCE to the start of common era, these texts are connected to the Vedic tradition. The most early colonial era Indology listed 10 Upanishads as Mukhya Upanishads.
The founders of the major schools of Vedanta, viz, Adi Shankara and Madhvacharya wrote bhāṣyas (commentaries) on these ten Principal Upanishads. The adjective mukhya means "principal", "chief", or "primary". The Mukhya Upanishads are accepted as śruti by all Hindus, or the most important scriptures of Hinduism.
The Principal Upanishads (1953) by Sarvepalli Radhakrishnan gives the text and English translation of a total of eighteen Upanishads, including the 13 listed by Hume (1921), plus Subāla, Jābāla, Paiṅgala, Kaivalya, Vajrasūcikā (Muktika nos. 30, 13, 59, 12 and 36).