The meridian 138° 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 138th meridian west forms a great circle with the 42nd meridian east.
Starting at the North Pole and heading south to the South Pole, the 138th meridian west passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Beaufort Sea | ||
| Yukon British Columbia — from | ||
| Alaska | ||
| Pacific Ocean | ||
| Southern Ocean | ||
| Antarctica | Unclaimed territory | |