The meridian 40° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, the Atlantic Ocean, South America, the Southern Ocean, and Antarctica to the South Pole. The 40th meridian west forms a great circle with the 140th meridian east.

From Pole to Pole

Starting at the North Pole and heading south to the South Pole, the 40th meridian west passes through: ! scope="col" width="120" | Co-ordinates ! scope="col" | Country, territory or sea ! scope="col" | Notes ! scope="row" style="background:#b0e0e6;" | Arctic Ocean ! scope="row" style="background:#b0e0e6;" | Lincoln Sea ! 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