Saint-Marc is a commune located in western Haiti within the Artibonite department. Geographically, it is situated at coordinates 19°7′N 72°42′W.
The city serves as one of the largest urban centers in the country, ranking second only to Gonaïves in size. It is positioned between the capital city of Port-au-Prince and Cap-Haïtien. According to the 2015 Census, the commune had a population of 266,642 inhabitants.