Kosala (kō´sələ), ancient Indian kingdom, corresponding roughly in area with the region of Oudh. Its capital was Ayodhya. It was a powerful state in the 6th cent. BC but was weakened by a series of wars with the neighboring kingdom of Magadha and finally (4th cent. BC) absorbed by it. Kosala was the setting of much Sanskrit epic literature including the Ramayana. Buddha and Mahavira, founder of Jainism, taught in the kingdom.