This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency-chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P = 1015). By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized. In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm.