The 180th meridian or antimeridian is the meridian which is 180° east or west of the Prime Meridian passing through the Royal Observatory, Greenwich. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.
Starting at the North Pole and heading south to the South Pole, the 180th meridian passes through:
| Co-ordinates (approximate) |
Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Russia | Wrangel Island | |
| Chukchi Sea | ||
| Russia | Chukotka Autonomous Okrug | |
| Bering Sea | ||
| Amchitka Pass | Passing just east of Semisopochnoi Island, Alaska, United States (at ) | |
| Pacific Ocean | Passing just east of Nukulaelae atoll, Tuvalu (at ) Passing just west of the island of Cikobia, Fiji (at ) |
|
| Fiji | Islands of Vanua Levu, Rabi, and Taveuni | |
| Pacific Ocean | Passing just east of the island of Moala, Fiji (at ) Passing just west of the island of Totoya, Fiji (at ) Passing just east of the island of Matuku, Fiji (at ) |
|
| Southern Ocean | ||
| Antarctica | Ross Dependency, claimed by New Zealand |
The meridian also passes between (but not particularly close to):
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