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