A steering control system comprises a steering component, a turning component, and a backup mechanism for alternately mechanically separating and linking steering and turning components. A steer-by-wire control unit is provided for executing steer-by-wire control of a turning actuator to a turning angle corresponding to a steering condition and control of a steering reaction force actuator for imparting steering reaction force corresponding to the turning condition. A steering assistance control unit is selectively linked to the backup mechanism to executing steering assistance control for at least one of the steering reaction force actuator and the turning actuator. A control switching unit is provided for controlling a shift, under predetermined conditions, between control by the steer-by-wire control unit and control by the steering assistance control unit.