Ans.

The Mahājanapadas (Sanskrit: महाजनपद, lit. 'great realm', from maha, "great", and janapada "foothold of a people") were sixteen kingdoms or oligarchic republics that existed in ancient India from the sixth to fourth centuries BCE. Two of them were most probably ganatantras (republics) and others had forms of monarchy. Ancient Buddhist texts like the Anguttara Nikaya make frequent reference to sixteen great kingdoms and republics which had evolved and flourished in a belt stretching from Gandhara in the northwest to Anga in the eastern part of the Indian subcontinent and included parts of the trans-Vindhyan region, prior to the rise of Buddhism in India.

The 6th–5th century BCE is often regarded as a major turning point in early Indian history; it saw the emergence of India's first large cities after the demise of the Indus Valley Civilization, as well as the rise of sramana movements (including Buddhism and Jainism) which challenged the religious orthodoxy of the Vedic Period.

Archaeologically, this period corresponds in part to the Northern Black Polished Ware culture.