Commonly known as AHJ, authority having jurisdiction is a term widely used in publications of the National Fire Protection Association and other organizations which write standards and codes. It refers to an organization, individual, or office responsible for approving equipment, installations, or procedures.
For example, an NFPA code might provide that an underground storage tank installation must be approved by the authority having jurisdiction. In one community, this authority could be the local fire marshal. In another, it could be the state environmental agency.