Abstract: A hypersonic scramjet engine fuel injector and a hypersonic scramjet engine having such a fuel injector. The engine has a serially connected inlet, combustor, and exhaust nozzle. Multiple, horizontally-spaced-apart fuel injectors are positioned in and connected to the combustor's top portion. Each fuel injector has a hollow wedge shape housing. To improve fuel-air mixing for better combustion, the housing's end wall has multiple, discrete, convergent-divergent fuel outlet nozzles and its side walls have horizontally-extending exterior grooves. Fuel is used to cool the fuel injector housing with the housing's bottom and side walls having fuel-exit holes and the housing having an interior serpentine fuel passageway.