eROSITA image of the region around the extremely bright Galactic black hole binary Cygnus X-1 in the 0.4–4 keV energy band. The image was saturated in the core to make very faint diffuse structures visible. In particular, the extended halo that is visible up to ~ 3 degrees from the source is due to X-ray photons scattered by mirrors only once (stray light). The same effect is largely responsible for a halo around Sco X-1 that is visible in the all-sky map. A special baffle mounted on top of eROSITA mirrors strongly reduces the magnitude of stray light, so that it is visible only around extremely bright objects. Theradial rays that are clearly seen in the image are due to the mirror support structure.