A catheter, more particularly an endovascular catheter, with a catheter shaft including a first lumen and a shaft opening, a deflection element and a controlling element. The first lumen and the shaft opening communicate with each other. The deflection element is rotatably arranged inside the catheter shaft, and configured to deflect a guidewire through the shaft opening. The controlling element is operably connected with the deflection element and configured to rotate the deflection element in a first rotating direction . Furthermore, the present invention refers to a catheter assembly with such a catheter and a guidewire.