A gas turbine engine is provided. The gas turbine engine includes a turbomachine having a compressor section, a combustor, and a turbine section arranged in serial flow order, the turbomachine further including an outer casing and, during operation of the gas turbine engine, an exhaust gas flow from the turbine section; and a fuel cell assembly positioned within the outer casing of the turbomachine, the fuel cell assembly having a fuel cell defining an inlet positioned to receive a portion of the exhaust gas flow, an outlet positioned to provide output products directly to the exhaust gas flow, or both.