The present invention relates to a system (1) for cleaning an optical sensor (3), notably of a motor vehicle, comprising: —an element (5) for spraying a cleaning liquid, —a tank (7) of cleaning liquid fluidically connected to the element (5) for spraying cleaning liquid, —a pump (9) configured to pump the cleaning liquid from the tank (7) to the element (5) for spraying the cleaning liquid, the system (1) also comprising a containment wall (11) for the cleaning liquid, which is movable between a retracted position in which the containment wall is configured to be positioned outside the field of view of the optical sensor (3) and a cleaning position in which the containment wall (11) is configured to be positioned in front of the optical sensor (3) so as to define a collection vessel (13) for the cleaning liquid, and in that it comprises an evacuation pipe (15) for the cleaning liquid that is connected both to the collection vessel (13) in the cleaning position and to the tank (7) of cleaning liquid.