A favourite was the intimate companion of a ruler or other important person. In post-classical and early-modern Europe, among other times and places, the term was used of individuals delegated significant political power by a ruler. It was especially a phenomenon of the 16th and 17th centuries, when government had become too complex for many hereditary rulers with no great interest in or talent for it, and political institutions were still evolving. From 1600 to 1660 there were particular successions of all-powerful minister-favourites in much of Europe, particularly in Spain, England, France and Sweden.

The term is also sometimes employed by writers who want to avoid terms such as "royal mistress", "friend", "companion", or "lover" (of any gender). Several favourites had sexual relations with the monarch (or the monarch's spouse), but the feelings of the monarch for the favourite could span the range from simple faith in the favourite's abilities to various degrees of emotional affection and dependence, and sometimes even encompassed sexual infatuation.

The term has an inbuilt element of disapproval and is defined by the Oxford English Dictionary as "One who stands unduly high in the favour of a prince", citing Shakespeare: "Like favourites/ Made proud by Princes" (Much Ado about Nothing, 3.1.9).