An umpire is an official in a variety of sports and competition, responsible for enforcing the rules of the sport, including sportsmanship decisions such as ejection.

The term derives from the Old French nonper, non, "not" and per, "equal": "one who is requested to act as arbiter of a dispute between two people". (as evidenced in cricket, where dismissal decisions can only be made on appeal). Noumper shows up around 1350 before undergoing a linguistic shift known as false splitting. It was written in 1426–1427 as a noounpier; the n was lost with the a indefinite article becoming an. The earliest version without the n shows up as owmpere, a variant spelling in Middle English, circa 1440. The leading n became permanently attached to the article, changing it to an Oumper around 1475.

The word was applied to the officials of many sports including baseball, association football (where it has been superseded by assistant-referee) and cricket (which still uses it).