A ring binder has housing including a central portion and lateral sides. Hinge plates are held between the lateral sides of the housing. Each of multiple rings includes at least one ring member mounted for movement with the hinge plates between closed and open positions. An actuator is mounted for pivotal movement relative to the housing and engageable with the hinge plates for opening rings. In one embodiment, the housing defines a stop engaged by the actuator upon arrival of the actuator at a terminal position when the actuator has opened the rings. The engagement between the surface of the actuator and the stop limits pivoting movement of the actuator relative to the housing in the opening direction beyond the terminal position. In another embodiment, the actuator is constructed for quicker response of the binder to movement of the actuator to open the rings.