Markstay-Warren is a town in the Canadian province of Ontario, located in the Sudbury District. Highway 17, from the city limits of Greater Sudbury to the Sudbury District's border with Nipissing District, lies entirely within Markstay-Warren. The town had a population of 2,297 in the Canada 2011 Census.
The town was created on January 1, 1999 by amalgamating the political townships of Ratter and Dunnet and Hagar, the geographic township of Awrey, and parts of the geographic townships of Hawley, Henry, Loughrin and Street. Along with the municipalities of St. Charles and French River, it is part of the region known as Sudbury East.