The meridian 21° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, Iceland, the Atlantic Ocean, the Southern Ocean, and Antarctica to the South Pole. The 21st meridian west forms a great circle with the 159th meridian east.

From Pole to Pole

Starting at the North Pole and heading south to the South Pole, the 21st meridian west passes through: ! scope="col" width="125" | Co-ordinates ! scope="col" | Country, territory or sea ! scope="col" | Notes ! scope="row" style="background:#b0e0e6;" | Arctic Ocean ! scope="row" | 🇬🇱 ! scope="row" style="background:#b0e0e6;" | Jokel Bay ! scope="row" | 🇬🇱 ! scope="row" style="background:#b0e0e6;" | Atlantic Ocean ! scope="row" | 🇮🇸 ! scope="row" style="background:#b0e0e6;" | Atlantic Ocean ! scope="row" style="background:#b0e0e6;" | Southern Ocean ! scope="row" | Antarctica