The meridian 99° 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 99th meridian west forms a great circle with the 81st meridian east.
Starting at the North Pole and heading south to the South Pole, the 99th meridian west passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Nunavut — Meighen Island | ||
| Peary Channel | ||
| Hassel Sound | ||
| Nunavut — Ellef Ringnes Island | ||
| Unnamed waterbody | ||
| Nunavut — Ricards Island and Bathurst Island | ||
| Parry Channel | Passing just west of Young Island, Nunavut, (at) Passing just east of Hamilton Island, Nunavut, (at) | |
| Nunavut — Russell Island, Mecham Island and Prince of Wales Island | ||
| Larsen Sound | ||
| Victoria Strait | ||
| Nunavut — King William Island | ||
| Queen Maud Gulf | ||
| Nunavut — O'Reilly Island | ||
| Queen Maud Gulf | ||
| Nunavut Manitoba — from, passing through Lake Winnipeg | ||
| North Dakota South Dakota — from Nebraska — from Kansas — from Oklahoma — from Texas — from | ||
| Tamaulipas Nuevo León — from Tamaulipas — from San Luis Potosí — from Hidalgo — from State of Mexico — from Hidalgo — from State of Mexico — from Mexico City — from Morelos — from Puebla — from Guerrero — from | ||
| Pacific Ocean | ||
| Southern Ocean | ||
| Antarctica | Unclaimed territory | |