An earl /ɜːrl/ is a member of the nobility. The title is Anglo-Saxon, akin to the Scandinavian form jarl, and meant "chieftain", particularly a chieftain set to rule a territory in a king's stead. In Scandinavia, it became obsolete in the Middle Ages and was replaced with duke (hertig/hertug). In later medieval Britain, it became the equivalent of the continental count (in England in the earlier period, it was more akin to duke; in Scotland it assimilated the concept of mormaer). However, earlier in Scandinavia, jarl could also mean sovereign prince. For example, the rulers of several of the petty kingdoms of Norway had in fact the title of jarl and in many cases of no lesser power than their neighbours who had the title of king. Alternative names for the "Earl/Count" rank in the nobility structure are used in other countries, such as Hakushaku during the Japanese Imperial era.

In modern Britain, an earl is a member of the peerage, ranking below a marquess and above viscount. A feminine form of earl never developed; countess is used as the equivalent feminine title.