A window restrictor that may be used to limit the opening of a window. The restrictor comprises a restrictor member and a latch mechanism. Typically, the restrictor member is attached to a stile or rail of the moving window pane and the latch mechanism is attached to a part of the casing or frame surrounding the window opening. In use, the restrictor member is engaged with the latch mechanism so that as the window is opened, the extent of opening is restricted by the restrictor member length. To fully open the window, the restrictor member is disengaged from the latch mechanism. When the restrictor member and latch mechanism are disengaged, they remain in such a configuration that, when the window is closed, the restrictor member and latch mechanism automatically re-engage to prevent the window being fully opened again. The restrictor member can comprise a hinged member which includes bias means.