Аннотация:The HI distribution in the region of the radio source Cygnus X and the supernova remnant G78.2+2.1 has been investigated using observations in the 21-cm radio line with an angular resolution of 2.4' obtained on the RATAN-600 radio telescope. Two HI shells can be distinguished: the first (diameter ~7deg ) surrounds the entire extended thermal radio source Cygnus X, while the second, smaller, one (diameter 2) envelops the supernova remnant. Both shells display expansion with velocities exceeding 10 km/s. To compare the HI and ionized-gas velocities, the region was observed in the Hα line with a Fabry-Perot interferometer and CCD array on the 125-cm telescope of the Crimean Laboratory of the Sternberg Astronomical Institute. The molecular-gas distribution around Cygnus X is considered on the basis of the CO line emission. The physical parameters of HI shells are determined, and their nature is discussed. The presence of a large HI shell and a cavity in the molecular-gas distribution around Cygnus X indicates that the radio source may form a single structure. The smaller HI shell around G78.2+2.1 could have been created by either the supernova explosion or the stellar wind of the precursor star.