He was a prophet of the ten-tribe kingdom of Israel, and predicted the restoration of the ancient boundaries (2 Kings 14:25-27) of the kingdom. This prophecy was fulfilled already during the reign of Jeroboam II, under whom Jonah exercised his ministry. Timewise this may mean he was contemporary with the prophets Hosea and Amos; or possibly he preceded them, and consequently may have been the very oldest of all the prophets whose writings we possess.
His personal history is mainly to be gathered from the Book of Jonah. It is chiefly interesting from the two-fold character in which he appears, (1) as a missionary to heathen Nineveh, and (2) as a type of the "Son of man".
Initial text from Easton's Bible Dictionary, 1897 -- Please update as needed