Nathu La(Tibetan: རྣ་ཐོས་ལ་, Wylie: Rna thos la, THL: Na tö la, Sikkimese: རྣ་ཐོས་ལ་) is a mountain pass in the Dongkya Range of the Himalayas between China's Yadong County in Tibet, and the Indian states of Sikkim. The pass, at 4,310 m (14,140 ft), connects the towns of Kalimpong and Gangtok to the villages and towns of the lower Chumbi Valley.

The pass was surveyed by J. W. Edgar in 1873, who described the pass as being used for trade by Tibetans. Francis Younghusband used the pass in 1903–04, as did a diplomatic British delegation to Lhasa in 1936–37, and Ernst Schäfer in 1938–39. In the 1950s, trade in the Kingdom of Sikkim used this pass. Diplomatically sealed by China and India after the 1962 Sino-Indian War, the pass saw skirmishes between the two countries in coming years, including the clashes in 1967 which resulted in fatalities on both sides. Nathu La has often been compared to Jelep La, a mountain pass situated at a distance of 3 miles (4.8 km).

The next few decades saw an improvement in ties leading to the re-opening of Nathu La in 2006. The opening of the pass provides an alternative route to the pilgrimage of Mount Kailash and Lake Manasarovar, and was expected to bolster the economy of the region by playing a key role in the growing Sino-Indian trade. However, while trade has had a net positive impact, it under-performed, and is limited to specific types of goods and to specific days of the week. Weather conditions including heavy snowfall restricts border trade to around 7 to 8 months.

Roads to the pass have been improved on both sides. Rail routes have been brought closer. It is part of the domestic tourist circuit in south-east Sikkim. Soldiers from both sides posted at Nathu La are among the closest along the entire Sino-India border. It is also one of the five Border Personnel Meeting points between the two armies of both countries. 2020 border tensions and the coronavirus pandemic have affected tourism and movement across the pass.

The name "Nathu La" is traditionally interpreted as "the whistling pass", or more commonly as the "listening ears pass". The Chinese government explains it as "a place where snow is deepest and the wind strongest". According to G. S. Bajpai, it means "flat ground from where the hill features gradually rise to right and left". Lepcha people who are native to the region call it ma-tho hlo/na tho lo; which may have possibly evolved to the present usage of the word.

Nathu La is a mountain pass on the Dongkya Range that separates Sikkim and the Chumbi Valley at an elevation of 14,250 feet (4,340 m). The pass is 52–54 kilometres (32–34 mi) east of Gangtok, the capital of Sikkim, and 35 kilometres (22 mi) from Yatung Shasima, the headquarters of the Yadong County (or the Chumbi Valley).

Nathu La is one of the three frequently-used passes between Sikkim and the Chumbi Valley, the other two being Cho La and Jelep La. Historically, Nathu La served Gangtok, while Cho La served the former Sikkim capital Tumlong and Jelep La served Kalimpong in West Bengal. Nathu La is mere 3 miles (4.8 km) northwest of Jelep La, as the crow flies, but the travel distance could be as much as 10 miles (16 km). On the Tibetan side, the Chola route led to Chumbi, the Nathu La route led to a village called Chema and the Jelep La route led to Rinchengang, all in the lower Chumbi Valley.

Even today, heavy snowfall causes the closure of the pass, with temperatures as low as −25 °C (−13 °F) and strong winds.