Ancient kingdom of India, situated in what is now west-central Bihar state, in northeastern India, in a strategic position in the Ganges River valley. It was the nucleus of several larger kingdoms or empires between the 6th century BC and the 8th century AD. It first flourished under Chandragupta and, later, Asoka, becoming the center of the vast and powerful Mauryan empire. Many sites in Magadha were sacred to Buddhism. Toward the close of the 12th century, Magadha was conquered by the Muslims.