Mukhya Upanishads, also known as Principal Upanishads, are the most ancient, widely studied Upanishads of Hinduism. Composed between 800 BCE to the start of common era, these texts are connected to the Vedic tradition. While some early colonial era Indology listed 10 Upanishads as Mukhya Upanishads, most scholars now consider the Principal Upanishads to be thirteen.
The first ten of the above Principal Upanishads were commented upon by the 8th century scholar Shankara. 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).