Vientiane (Lao: ວຽງຈັນ, romanized: Wiang Chan, pronounced [wíaŋ tɕàn]) is the capital and largest city of Laos. Situated on the banks of the Mekong River at the Thai border, it comprises the five urban districts of Vientiane Prefecture and had a population of 840,000 as of the 2023 Census. Established as the capital of the Kingdom of Lan Xang in 1563, Vientiane served as the administrative center during French rule and retains colonial-era architecture alongside Buddhist landmarks such as Pha That Luang, a national symbol of Buddhism, and Haw Phra Kaew, which once housed the Emerald Buddha until its 18th-century relocation to Thailand.

Vientiane emerged as a significant settlement in the 16th century as part of the Lan Xang Kingdom. Over time, Vientiane developed into an important regional center, serving as the kingdom’s administrative and cultural hub. However, the city experienced periods of turmoil, including invasions by the Siamese (Thai) kingdom in the late 18th and early 19th centuries, which resulted in its temporary decline. In the late 19th century, Vientiane became part of French Indochina under colonial rule, which introduced European architecture and infrastructure. After Laos gained independence in 1953, Vientiane was established as the nation’s capital and has since grown into the political, economic, and cultural heart of the country.

Vientiane is located in the western part of Laos, on the eastern bank of the Mekong River, which forms the natural border with Thailand. The city sits on a low, flat plain surrounded by low hills to the east, providing a natural geographical boundary. Its position along the Mekong has made Vientiane a key trading and transportation hub throughout its history. The city experiences a tropical wet and dry climate, with a distinct rainy season from May to October and a dry season from November to April. The riverfront and flat terrain have influenced both the urban layout and the development of agricultural activities in the surrounding region.

The city functions as Laos' political, economic and transportation hub, emphasizing regional connectivity through infrastructure projects like the Laos–China Railway (LCR). This railway, a component of China's Belt and Road Initiative, terminates in Vientiane after linking Kunming, China, and is slated to connect to Thailand’s rail network via the Mekong Railway Bridge.