Endovascular techniques have been increasingly adapted to medical applications as a minimally-invasive treatment approach to diagnose and treat various vascular diseases. Guidewires are the basic devices in endovascular surgery. The conventional practice of endovascular procedures has a number of drawbacks such as prolonged exposure to high doses of X-ray radiation, long operation time and undesired damage by surgeon’s unskilled operation. In this letter, we proposed a magnetically steerable guidewire and designed a three-dimensional magnetically actuating system. The proposed magnetically steerable guidewire consists of a commercial guidewire connecting to a soft actuator made of Ecoflex and magnetic powder. The actuating system contains two symmetrical parts, each consisting of three linear motors. It has great workspace of 700 mm × 500 mm × 500 mm, which can help the proposed guidewire to achieve a wide range of deflection angle. The relationship between the proposed guidewire’s deflection angle and the magnitude of the external magnetic field are explored, as well as the direction of the magnetic field. The proposed guidewire is flexible enough to make sharp turns up to 180${}^{\circ }$ in three dimensional workspace. The guidewire has achieved navigating through a set of rings and in a complex and constrained vascular phantom by programmed actuating magnetic fields.