Fluoride salt-cooled high-temperature reactors (FHRs) represent a promising technology. Significant knowledge gaps to implementation may be addressed via a small-scale demonstration reactor (DR) to increase the technology readiness level (TRL) of the system for the longer term. This paper outlines a notional concept and addresses how the concept would advance the TRL of FHR concepts. This notional concept is under development as part of a U.S. Department of Energy Office of Nuclear Energy study of options for advanced test and demonstration reactor systems. Development of the FHR DR will enable commercial FHR deployment through disruptive and rapid technology development and demonstration, closing gaps to commercial viability. Lower risk technologies in the initial design help ensure that the reactor is built, licensed, and operated within an acceptable budget and schedule. Important capabilities to be demonstrated by building and operating the FHR DR include core design methodologies; fabrication and operation of high temperature reactors; salt procurement, handling, maintenance and ultimate disposal; salt chemistry control to maximize vessel life; tritium management; heat exchanger performance (including passive decay heat removal); pump performance; and reactivity control. The FHR DR is part of the broader FHR technology development and demonstration efforts already underway. Nonreactor test efforts (e.g., heated salt loops or loops using simulant fluids) can demonstrate technologies necessary for commercial deployment of FHRs. The FHR DR advances the technical maturity and readiness level of the system.