Savannakhet (ສະຫວັນນະເຂດ sā.wǎn.nā.khȅːt), officially named Kaysone Phomvihane (ໄກສອນ ພົມວິຫານ); since 2005 and previously known as Khanthaboury (ຄັນທະບູລີ), is a city in western Laos. It is the capital of Savannakhet Province. With a population of 125,760 (2018), it is the second-largest city in Laos, after Vientiane. Although the old French colonial quarter of the town, along the Mekong River-front, is depressed and crumbling, the town's proximity to Thailand's booming economy has brought about new commercial development in the northern part of the town, near both the river crossing and the bus terminal.
Like all Lao cities, Savannakhet has a mixed population of Lao, Thai, Vietnamese and Chinese, as well as minority peoples from the Lao interior. It has a large 15th-century Buddhist temple, Wat Sainyaphum, a Chinese temple, the Catholic Co-Cathedral of St. Therese and a mosque. The Second Thai–Lao Friendship Bridge over the Mekong connects to Mukdahan Province in Thailand. The two-lane, , bridge opened to the general public on 9 January 2007.
The annual per capita income of Kaysone Phomvihane City is US$2,041 (2018).
The settlement of Savannakhet was formerly called Khanthaboury. Then it became Savannakhet. Its name was changed to Kaysone Phomvihane in 2005, while retaining its status as the provincial capital of Savannakhet Province. The city is the birthplace of Kaysone Phomvihane, the first leader of Laos from 1975 to 1992 after the dissolution of the Kingdom of Laos. In 2018, its status was upgraded to that of a "city". In order to attain city status, a district or municipality must be financially self-sufficient and have a population of at least 60,000 persons.
The city is served by Savannakhet Airport.
Savannakhet features a tropical savanna climate (Aw) according to Köppen climate classification with a little subtropical climate characteristics as the city located 16.5° north of the equator. The hottest month is April (mean = ) with temperature ranging from to , while the coolest month is December (mean = ) with temperature ranging from to .