A hostage is a person or entity which is held by one of two belligerent parties to the other or seized as security for the carrying out of an agreement, or as a preventive measure against war. However, in contemporary usage, it means someone who is seized by a criminal abductor in order to compel another party such as a relative, employer, law enforcement, or government to act, or refrain from acting, in a particular way, often under threat of serious physical harm to the hostage(s) after expiration of an ultimatum.

A person who seizes one or more hostages is known as a hostage-taker; if the hostages are present voluntarily, then the receiver is known as a host.