FDX may refer to: FedEx Corporation, original FDX Corporation, American logistics services company FedEx Express, the ICAO code FDX, American cargo airline
Computing: FDX, an expansion pack for the 1980s Memotech MTX computer .fdx, the filename extension for Final Draft files Fetch-decode-execute cycle, or FDX, basic operation cycle of a computer
Telecommunications: Full-duplex, communication circuit