The meridian 166° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole.
The 166th meridian west forms a great circle with the 14th meridian east.
Starting at the North Pole and heading south to the South Pole, the 166th meridian west passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Chukchi Sea | ||
| Alaska | ||
| Chukchi Sea | ||
| Bering Sea | ||
| Alaska — Seward Peninsula | ||
| Bering Sea | Passing just east of Sledge Island, Alaska, (at) | |
| Alaska — Krekatok Island, Neragon Island and the mainland | ||
| Bering Sea | ||
| Alaska — Nunivak Island | ||
| Bering Sea | ||
| Alaska — Akutan Island | ||
| Pacific Ocean | Passing just east of Unalga Island, Alaska, (at) Passing just east of Sedanka Island, Alaska, (at) Passing just east of the French Frigate Shoals, Hawaii, (at) Passing just west of Pukapuka atoll, (at) | |
| Southern Ocean | ||
| Antarctica | Ross Dependency, claimed by | |