Common Rail Injector direct fuel injection is a direct fuel injection system for diesel engines.

On diesel engines, it features a high-pressure (over 100 bar or 10 MPa or 1,500 psi) fuel rail feeding solenoid valves, as opposed to a low-pressure fuel pump feeding unit injectors (or pump nozzles). Third-generation common-rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 2,500 bar (250 MPa; 36,000 psi).

High pressure injection delivers power and fuel consumption benefits over earlier lower pressure fuel injection, by injecting fuel as a larger number of smaller droplets, giving a much higher ratio of surface area to volume. This provides improved vaporization from the surface of the fuel droplets, and so more efficient combining of atmospheric oxygen with vaporized fuel delivering more complete combustion.