The invention relates to a device for fixing a windscreen wiper (16) to a drive arm (12) of a wiping system (10), said device comprising a terminal part (14) of an arm (12), a connector (20) intended to be fixed to the wiper (16), a coupling adapter (50) for coupling the connector (20) to said arm (12), and an intermediate part (40), said adapter (50) comprising means for holding it onto the arm in a nominal immobilizing position, said intermediate part (40) being mobile in said terminal part (14) relative to the adapter (50), and comprising means for releasing and/or locking said holding means, so as to allow the adapter (50) to be mounted on and/or removed from the arm (12) and/or so as to retain the adapter (50) on the arm (12) in the nominal immobilizing position.The invention also relates to a wiping system (10) comprising such a fixing device.