An agent provocateur (French for 'inciting agent') is a person who commits, or who acts to entice another person to commit, an illegal or rash act or falsely implicates them in partaking in an illegal act, so as to ruin the reputation of, or entice legal action against, the target, or a group they belong to or are perceived to belong to. They may target any group, such as a peaceful protest or demonstration, a union, a political party or a company.

In jurisdictions in which conspiracy is a serious crime in itself, it can be sufficient for the agent provocateur to entrap the target into discussing and planning an illegal act. It is not necessary for the illegal act to be carried out or even prepared.

Prevention of infiltration by agents provocateurs is part of the duty of demonstration marshals, also called stewards, deployed by organizers of large or controversial assemblies.