Chandogya Upanishad is as old as Brhadaranyaka Upanishad and together they rank among the oldest Upanishads. Chandogya Upanishad was written on the Vedic Brahmana period about ninth to eighth century BC. Chandogya Upanishad is associated with Samveda. It is ranked ninth in the Muktika canon of hundred and eight Upanishadas.
