The meridian 18° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, Iceland, the Atlantic Ocean, the Canary Islands, the Southern Ocean, and Antarctica to the South Pole.
The 18th meridian west forms a great circle with the 162nd meridian east.
Starting at the North Pole and heading south to the South Pole, the 18th meridian west passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Prinsesse Margrethe Island, Prinsesse Dagmar Island, and mainland | ||
| Atlantic Ocean | Greenland Sea | |
| Atlantic Ocean | Greenland Sea | |
| Ile de France | ||
| Atlantic Ocean | Greenland Sea | |
| Shannon Island | ||
| Atlantic Ocean | Greenland Sea | |
| Island of Grímsey | ||
| Atlantic Ocean | ||
| Atlantic Ocean | ||
| Island of La Palma | ||
| Atlantic Ocean | ||
| Island of El Hierro | ||
| Atlantic Ocean | ||
| Southern Ocean | ||
| Antarctica | Queen Maud Land, claimed by | |