What is Jarl (title)?

Jarl is a rank of the nobility in Scandinavia. In Old Norse, it meant "chieftain", particularly a chieftain set to rule a territory in a king's stead. Jarl could also mean a sovereign prince. For example, the rulers of several of the petty kingdoms of Norway had the title of jarl and in many cases they had no less power than their neighbours who had the title of king. It became obsolete in the Middle Ages and was replaced by duke. The word is etymologically related to the English earl.