The Atlantic World, a pentagonal region encompassing one twelfth of the Earth, includes the Azores, Madeira, northwestern Europe (including western Denmark and western Norway), the British Isles, the Orkney Islands, the Shetland Islands, the Faroe Islands, Iceland, Greenland, Newfoundland, eastern and central North America, the northern section of Hispaniola, and several smaller island groups, notably Bermuda, the Bahamas, and the Turks and Caicos.

The eastern boundary, marked at 10° east longitude, divides Scandinavia into Eastern and Western sections, with Western Scandinavia oriented toward the North Atlantic and Eastern Scandinavia centered on the Baltic Sea Basin. This boundary also aligns with the historical eastern border of West Germany (1949–1990), before terminating in south-central Germany at its junction with the neighboring region to the southeast.

The western boundary, at 110° west longitude, cuts through Canada, separating the northern districts of Nunavut and the Northwest Territories from Alberta and Saskatchewan, approximately 75 miles south of the Alberta-Saskatchewan-Montana junction (48.1896851°N)—the northernmost point of the neighboring world to the southwest.

The southwestern boundary follows the division between the upper and lower Mississippi River Basin, then extends eastward into the Atlantic Ocean just south of Jacksonville, Florida, before terminating in northwestern Hispaniola.