St. Louis County is a county located in the Arrowhead Region of the U.S. state of Minnesota. As of the 2020 census, the population was 200,231. Its county seat is Duluth. It is the largest county in Minnesota by land area, and the largest in the United States by total area east of the Mississippi River. St. Louis County is included in the Duluth, MN–Superior, WI Metropolitan Statistical Area.

The Arrowhead Region is located in the northeastern part of the U.S. state of Minnesota, so called because of its pointed shape. The predominantly rural region encompasses 10,635.26 square miles (27,545.2 km2) of land area and includes Carlton, Cook, Lake and Saint Louis counties. Its population at the 2000 census was 248,425 residents. The region is loosely defined, and Aitkin, Itasca, and Koochiching counties are sometimes considered as part of the region, increasing the land area to 18,221.97 square miles (47,194.7 km2) and the population to 322,073 residents. Primary industries in the region include tourism and iron mining.