The invention relates to a valve (10) for regulating oxygen in a fuel cell system (11), comprising: —a valve housing (12), which has a valve seat (13) and a through-opening (14) in the valve seat (13); —a valve shaft (15), which has a valve disk (16) formed thereon for closing the through-opening (14) in the valve seat (13) in a closed state of the valve (10) and for releasing the through-opening (14) in a released state of the valve (10); and—a moving means (17) for linearly moving the valve disk (16) between an opening position in an open state, in which open state the valve disk (16) is spaced apart from the valve seat (13), and a closing position in the closed state, in which closed state the valve disk (16) is positioned on the valve seat (13), and for rotationally moving the valve shaft (15) in order to pivot the valve disk (16) between the opening position and a releasing position in the released state, in which released state at least part of the valve disk (16) is spaced farther apart from the valve seat (13) than in the opening position. The invention also relates to a fuel cell system (11) comprising at least one valve (10) according to the invention.