The meridian 121° 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 121st meridian west forms a great circle with the 59th meridian east.

From Pole to Pole

Starting at the North Pole and heading south to the South Pole, the 121st meridian west passes through: ! scope="col" width="130" | 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;" | M'Clure Strait ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Amundsen Gulf ! scope="row" | 🇨🇦 ! scope="row" | 🇺🇸 ! scope="row" style="background:#b0e0e6;" | Pacific Ocean ! scope="row" style="background:#b0e0e6;" | Southern Ocean ! scope="row" | Antarctica