We have analyzed a Chandra /HETGS spectrum of the Galactic black hole Cygnus X-1 , obtained at a source flux which is approximately twice that commonly observed in its persistent low-intensity , spectrally-hard state . We find a myriad of absorption lines in the spectrum , including Ly- \alpha lines and helium-like resonance lines from Ne , Na , Mg , and Si . We calculate a flux-weighted mean red-shift of \simeq 100 km/s and a flux-weighted mean velocity width of \simeq 800 km/s ( FWHM ) for lines from these elements . We also detect a number of transitions from Fe XVIII–XXIV and Ni XIX–XX in absorption ; however , the identification of these lines is less certain and a greater range of shifts and breadth is measured . Our observation occurred at a binary phase of \phi \simeq 0.76 ; the lines observed are consistent with absorption in an ionized region of the supergiant O9.7 Iab companion wind . The spectrum is extremely complicated in that a range of temperatures and densities are implied . Prior Chandra /HETGS spectra of Cygnus X-1 were obtained in a similar transition state ( at \phi \simeq 0.93 ) and in the low/hard state ( at \phi \simeq 0.84 ) . Considered together , these spectra provide evidence for a companion wind that is focused as it flows onto the black hole primary in this system .