Saint Ignace, usually written as St. Ignace, is a city at the southern tip of the Upper Peninsula of the U.S. state of Michigan, bordering the Straits of Mackinac. The population was 2,452 at the 2010 census. It is the county seat of Mackinac County. For travelers coming from the Lower Peninsula, St. Ignace is the gateway to the northern part of the state.