The meridian 109° 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 109th meridian west forms a great circle with the 71st meridian east. In the United States, the western boundaries of Colorado and New Mexico and the eastern boundaries of Utah and Arizona lie on the 32nd meridian west from Washington, which is approximately 3 minutes of longitude west of the 109th meridian west of Greenwich, or approximately 2.5 mi.

From pole to pole

Starting at the North Pole and heading south to the South Pole, the 109th 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" | Canada ! scope="row" style="background:#b0e0e6;" | Sabine Bay ! scope="row" | Canada ! scope="row" style="background:#b0e0e6;" | Parry Channel ! scope="row" | Canada ! scope="row" style="background:#b0e0e6;" | Dease Strait ! scope="row" style="background:#b0e0e6;" | Bathurst Inlet ! scope="row" | Canada ! scope="row" | United States ! scope="row" | Mexico ! scope="row" style="background:#b0e0e6;" | Pacific Ocean ! scope="row" style="background:#b0e0e6;" | Southern Ocean ! scope="row" | Antarctica