An autonomous vacuum cleaner operable to navigate about a surrounding environment to perform a surface cleaning operation without continuous human input. The vacuum cleaner includes a suction nozzle and a suction motor and a fan assembly operable to generate an airflow through the vacuum cleaner from the suction nozzle through a debris separator to a clean air exhaust. The suction motor and the fan assembly having an axis of rotation and a fan of the fan assembly rotatable about the axis of rotation. The axis of rotation is orientated horizontally. The debris separator includes a cyclonic separator operable to separate debris from the airflow and the cyclonic separator includes a cylindrical wall along a longitudinal axis, the longitudinal axis of the cyclonic separator being orientated horizontally.