Medical fluid connector for a medical fluid line system, having a first body with a tube section which extends in an axial direction and which forms a fluid channel with an inlet, and with a first thread, which is oriented so as to be coaxial with the tube section, and a second body with a lumen which extends in axial direction and which engages around the tube section in a circumferential direction and which has an outlet which is associated with the inlet, and with a second thread, which interacts with the first thread of the first body in a manner movable by screwing, wherein the fluid connector is, by means of a relative screwing movement between the first body and the second body, able to be transferred between a closed position, in which the lumen and the tube section interact so as to form a sealing connection which, in a fluid-tight manner, seals off the outlet, and an open position, in which the sealing connection is eliminated and the outlet is connected in a fluid-conducting manner to the inlet, and wherein the second body has a third thread, which is oriented so as to be coaxial with the first thread and with the second thread and is designed to rotate in the opposite direction in relation to said first and second threads, characterized in that provision is made of a closure cap with a fourth thread which in a delivery state of the fluid connector is detachably screwed to the third thread of the second body, wherein the fluid connector assumes the open position, and wherein the outlet is closed off in an air-permeable and liquid-tight manner by means of the closure cap. a first body with a tube section which extends in an axial direction and which forms a fluid channel with an inlet, and with a first thread, which is oriented so as to be coaxial with the tube section, and a second body with a lumen which extends in axial direction and which engages around the tube section in a circumferential direction and which has an outlet which is associated with the inlet, and with a second thread, which interacts with the first thread of the first body in a manner movable by screwing, wherein the fluid connector is, by means of a relative screwing movement between the first body and the second body, able to be transferred between a closed position, in which the lumen and the tube section interact so as to form a sealing connection which, in a fluid-tight manner, seals off the outlet, and an open position, in which the sealing connection is eliminated and the outlet is connected in a fluid-conducting manner to the inlet, and wherein the second body has a third thread, which is oriented so as to be coaxial with the first thread and with the second thread and is designed to rotate in the opposite direction in relation to said first and second threads, a closed position, in which the lumen and the tube section interact so as to form a sealing connection which, in a fluid-tight manner, seals off the outlet, and an open position, in which the sealing connection is eliminated and the outlet is connected in a fluid-conducting manner to the inlet, and wherein the second body has a third thread, which is oriented so as to be coaxial with the first thread and with the second thread and is designed to rotate in the opposite direction in relation to said first and second threads, characterized in that provision is made of a closure cap with a fourth thread which in a delivery state of the fluid connector is detachably screwed to the third thread of the second body, wherein the fluid connector assumes the open position, and wherein the outlet is closed off in an air-permeable and liquid-tight manner by means of the closure cap.