The authors measured atomic hydrogen, the principal component of the interstellar medium in the Milky Way, over a five-year period using the 25-meter radio telescope of the Netherlands Foundation for Research in Astronomy. Displayed in several projections, each map corresponds to a particular velocity interval; separation by velocity roughly corresponds to separation by distance, or by energetics. The Leiden/Dwingeloo survey covers the entire sky above declination -300, on a half-degree grid, over a velocity range of 1000 km/s at 1 km/s resolution. The limiting brightness temperature sensitivity is 0.07 K. A CD-ROM also accompanies the Atlas, and contains the entire dataset of the Leiden/Dwingeloo survey in computer-readable form. The CD-ROM also contains color images in GIF format, as well as animations displaying the 3-dimensional data cube.