The meridian 100° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole.
The 100th meridian east forms a great circle with the 80th meridian west.
Starting at the North Pole and heading south to the South Pole, the 100th meridian east passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Arctic Ocean | ||
| Laptev Sea | ||
| Krasnoyarsk Krai — October Revolution Island, Severnaya Zemlya | ||
| Kara Sea | ||
| Krasnoyarsk Krai — Bolshevik Island, Severnaya Zemlya | ||
| Kara Sea | ||
| Krasnoyarsk Krai Irkutsk Oblast — from Republic of Buryatia — from | ||
| Inner Mongolia Gansu — from Inner Mongolia — from Gansu — from Qinghai — from Sichuan — from Yunnan — from | ||
| (Burma) | ||
| Gulf of Thailand | ||
| Gulf of Thailand | ||
| Islands of Ko Pha Ngan and Ko Samui | ||
| Gulf of Thailand | ||
| Strait of Malacca | Passing just east of the Langkawi islands, (at) Passing just west of Penang Island, (at) | |
| Island of Sumatra | ||
| Indian Ocean | ||
| Island of North Pagai | ||
| Indian Ocean | ||
| Southern Ocean | ||
| Antarctica | Australian Antarctic Territory, claimed by | |