Multiple observations of Cygnus X-1, Cygnus X-2, and Cygnus X-3 were carried out with the Bragg crystal polarimeters aboard OSO 8. Of these sources, an unambiguous detection of the time-averaged polarization was obtained only for Cygnus X-1, which has a polarization of 2.4% plus or minus 1.1% at 2.6 keV and 5.3% plus or minus 2.5% at 5.2 keV. While statistically significant evidence for polarization of Cygnus X-2 of 4.9% at 2.6 keV was obtained in a 1975 observation, this result was not confirmed in later observations. For Cygnus X-3, modulation of the observed flux at twice the rotation frequency of the satellite, the signature of polarization, was also detected, but spurious modulation due to the presence of additional sources in the field of view cannot be ruled out.