A queen bee is typically an adult, mated female (gyne) that lives in a colony or hive of honey bees. With fully developed reproductive organs, the queen is usually the mother of most, if not all, of the bees in the beehive. Queens are developed from larvae selected by worker bees and specially fed in order to become sexually mature. There is normally only one adult, mated queen in a hive, in which case the bees will usually follow and fiercely protect her.

The term "queen bee" can be more generally applied to any dominant reproductive female in a colony of a eusocial bee species other than honey bees. However, as in the Brazilian stingless bee Schwarziana quadripunctata, a single nest may have multiple queens or even dwarf queens, ready to replace a dominant queen in a case of sudden death.