Savannakhet, officially named Kaysone Phomvihane ; 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.

Savannakhet is a province of Laos. The name derives from Savanh Nakhone the province's original name. It bears the same meaning as Nakhon Sawan, a city in Thailand.