Phu Bai Combat Base is a former U.S. Army and U.S. Marine Corps base south of Huế, in central Vietnam. The Army Security Agency, operating under cover of the 3rd Radio Research Unit, established a radio facility at Phu Bai in 1963, 12 km southeast of Huế on Highway 1. The operational unit was later redesignated as the 8th Radio Research Field Station.