The 129th meridian east is a line of longitude extending from the North Pole across the Arctic Ocean, Asia, the Pacific Ocean, Australia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole.
Like all meridians, it is half of a great circle. Its length is 20,003.932 kilometres (12,429.873 mi), which is half the Earth's circumference. It forms a great circle with the 51st meridian west.
The 129th meridian east passes through:
- North Pole
- Arctic Ocean
- Russia (Sakha Republic, Magadan Oblast)
- Sea of Okhotsk
- Russia (Kuril Islands – Urup Island)
- Pacific Ocean (passing east of the Korean Peninsula and Japan)
- East China Sea
- Philippines (passing through the eastern part of Luzon island)
- Pacific Ocean (Philippine Sea)
- Indonesia (passing through the island of Halmahera, Ceram, and the Aru Islands)
- Arafura Sea
- Australia (passing through the Northern Territory and Western Australia, including the Great Sandy Desert, Gibson Desert, and Nullarbor Plain)
- Indian Ocean (Great Australian Bight)
- Southern Ocean
- Antarctica (specifically Wilkes Land)
- South Pole
The meridian is used to define geographical locations and, in conjunction with other meridians, can be used for time zone calculations. For example, in Australia, the border between Western Australia and the Northern Territory roughly follows this meridian for a significant distance.