Emir (; Arabic: أمير ʾamīr [ʔaˈmiːr]), sometimes transliterated amir, amier, or ameer, is a word of Arabic origin that can refer to a male monarch, aristocrat, holder of high-ranking military or political office, or other person possessing actual or ceremonial authority. The title has a long history of use in the Arab World, East Africa, West Africa, Central Asia, and the Indian subcontinent. In the modern era, when used as a formal monarchical title, it is roughly synonymous with "prince", applicable both to a son of a hereditary monarch, and to a reigning monarch of a sovereign principality, namely an emirate. The feminine form is emira (أميرة ʾamīrah), a cognate for "princess". Prior to its use as a monarchical title, the term "emir" was historically used to denote a "commander", "general", or "leader" (for example, Amir al-Mu'min). In contemporary usage, "emir" is also sometimes used as either an honorary or formal title for the head of an Islamic, or Arab (regardless of religion) organisation or movement.

Qatar and Kuwait are the only independent countries which retain the title "emir" for their monarchs. In recent years, the title has been gradually replaced by "king" by contemporary hereditary rulers who wish to emphasize their secular authority under the rule of law. A notable example is Bahrain, whose monarch changed his title from emir to king in 2002.