The meridian 90° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Gulf of Mexico, Central America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole.
In Antarctica, the meridian defines the western limit of Chile's territorial claim. The land further west is not claimed by any nation.
The 90th meridian west forms a great circle with the 90th meridian east.
This meridian is halfway between the Prime meridian and the 180th meridian and the center of the Western Hemisphere is on this meridian.