Mahājanapadas (Sanskrit: महाजनपद, Mahājanapadas), literally "great realms", (from maha, "great", and janapada "foothold of a tribe", "country") were ancient Indian kingdoms or countries. Ancient Buddhist texts like Anguttara Nikaya make frequent reference to sixteen great kingdoms and republics (Solas Mahajanapadas) 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 sixth century BCE is often regarded as a major turning point in early Indian history.

The political structure of the ancient Indians appears to have started with semi-nomadic tribal units called Jana (meaning "people" or by extension "ethnic group" or "tribe"). Early Vedic texts attest several Janas or tribes of the Indo-Aryans, living in a semi-nomadic tribal state and fighting among themselves and with other Non-Aryan tribes for cows, sheep and green pastures. These early Vedic Janas later coalesced into the Janapadas of the Epic Age.