The present invention relates to a braking device and to a braking system, each having a master brake cylinder (10) having at least one first pressure chamber (12) that is subdivided or is able to be subdivided at least into a first partial volume (12a) and a second partial volume (12b), which are hydraulically connectable or connected to a brake fluid reservoir (24), a first brake circuit (28) being hydraulically connectable or connected to the first partial volume (12a), and having a valve device (38) that is mechanically designed in such a way that a pressure buildup up to a mechanically specified limit pressure may be brought about in the second partial volume (12b), brake fluid being transferable at least into the first brake circuit (28) via at least one subcomponent (38a) of the valve device (38), and an exceeding of the limit pressure in the second partial volume (12b) being prevented.