What is a person who goes on a mission called?

A person who goes on a mission is often referred to as a "missionary" if their purpose is religious or spiritual. In a broader context, they can be called an "agent," "envoy," or "delegate," depending on the nature of the mission. Additionally, in military or exploratory contexts, they may be termed "operatives" or "expeditions." The specific term can vary based on the mission's goals and context.