Muang Sing is a small town and district in Luang Namtha Province, northwestern Laos, about 60 kilometres northwest of the town of Luang Namtha and 360 kilometres northwest of Vientiane. It lies very close to the border with Yunnan, China, surrounded by mountains and rivers. Historically, Muang Sing has been a major producer of opium and still has problems with drugs and smuggling, due to its proximity to China and Myanmar.