A city gate is a gate that forms or was part of the wall of a city.

City gates were traditionally built to serve as a controlled entry and exit point from a walled city for people, vehicles, goods and animals. Depending on the historical context, they have fulfilled functions related to defense, security, health, commerce, taxes and representation, and were consequently supervised by military or municipal authorities. Doors were also frequently used to display different types of public information such as notices, taxes, tolls, local measurement standards or legal texts. They could be heavily fortified, decorated with heraldic shields, sculptures or inscriptions or used to warn or intimidate, for example by showing the heads of decapitated criminals or public enemies.

City gates, in one form or another, can be found all over the world in cities from ancient times to around the 20th century. Many cities closed their doors after a curfew each night, for example Prague.

When they had more stability and freedom, many walled cities demolished their fortifications, such as gates, although many still survive, for historical interest rather than security. Many gates have been restored or rebuilt, or new gates have been built to improve the appearance of the city, such as Bab Bou Jalous in Fez "Fez (Morocco)"). With increased levels of traffic, city gates have been threatened in the past by impeding the flow of traffic, for example Temple Bar "Temple Bar (London)") in London, which was demolished in the 19th century.