| Saint-Ghislain | |
| Picture-Legend: | Saint-Ghislain: the former town hall (1752), the new church, and the tower of the old church (16th century) |
| Map: | Saint-Ghislain_Hainaut_Belgium_Map.svg |
| Map-Legend: | Location of Saint-Ghislain in Hainaut |
| Arms: | Blason ville be Saint-Ghislain.svg |
| Flag: | Flag of Saint-Gilles-lez-Bruxelles.svg |
| Arrondissement: | Mons |
| Nis: | 53070 |
| Mayor: | Daniel Olivier (PS) |
| Majority: | PS - MR & Citoyens |
| Postal-Codes: | 7330-7334 |
| Telephone-Area: | 065 |
| Web: | www.saint-ghislain.be |
| Coordinates: | 50.45°N 52°W |
Saint-Ghislain (in French pronounced as /sɛ̃ ɡilɛ̃/; Saint-Guilagne; Walloon: Sint-Guilin) is a city and municipality of Wallonia located in the province of Hainaut, Belgium.
On 1 January 2018 the municipality had 23,335 inhabitants. The total area is, giving a population density of .
The municipality consists of the following districts: Baudour, Hautrage, Neufmaison, Saint-Ghislain, Sirault, Tertre et Villerot.
The town is named after Saint Ghislain. In the 7th century, with two unknown disciples Ghislain made a clearing in the vicinity of Castrilocus (now Mons), later taking up his abode at a place called Ursidongus, where he built an oratory or chapel dedicated to Saints Peter and Paul. Ursidongus was later named after him.
Google chose Saint-Ghislain in 2007 to host its new major European datacenter.