One of the four great mahajanapadas of ancient India and a major power of the 6th–4th centuries BCE, neighbor and rival of Magadha, set at the edge of the 600 BCE deep-time layer cutoff.
Conquered and absorbed by Magadha under the Haryanka dynasty's king Ajatashatru c. 449–400 BCE, after a series of wars that ended Kosala's independence; the kingdom was not conquered by the Nanda dynasty.
Standard reference for Kosala and the Mahajanapada period.
Era/regional: covers the great mahajanapadas of the 6th-4th centuries BCE, including Kosala and its rivalry with Magadha.
The Ramayana is traditionally set at Ayodhya, capital of the Kosala kingdom; this is legendary/epic literature of uncertain historicity attached to the earliest attested kingdom of that name/region, and may already be covered elsewhere in the reading lists.