The Sơn Tây campaign was a campaign fought by the French to capture the strategically important city of Sơn Tây in Tonkin from Liu Yongfu's Black Flag Army and allied contingents of Vietnamese and Chinese troops. The campaign was one of several clashes between the Tonkin Expeditionary Corps and the Black Flag Army during the Tonkin campaign (1883–1886), and took place during the period of undeclared hostilities that preceded the Sino-French War.

Sơn Tây is a district-level town in Hanoi, the capital of Vietnam. It was the capital of Sơn Tây province before merging with Hà Đông province to form Hà Tây province in 1965. Sơn Tây lies 35 km west of the capital Hanoi. It had a city status in Hà Tây province. However, when Hà Tây was absorbed into Hanoi, Sơn Tây was demoted from a city to a town.