Northwest Indiana, commonly referred to as "The Region" after the Calumet Region, is an unofficial geographic area in the northwestern corner of Indiana in the United States. Although its boundaries are not formally defined, the area is generally associated with the Gary, Indiana Metropolitan Division, which includes Jasper, Lake, Porter and Newton counties, and the Michigan City–La Porte Metropolitan Statistical Area, which includes LaPorte County, with some broader definitions also including Starke and Pulaski counties.
The area borders Lake Michigan and portions of it are considered part of the Chicago metropolitan area. Based on the 2020 United States census, the broadest definition of Northwest Indiana has a population of 866,965, making it the second-largest urban area in the state after the Indianapolis metropolitan area.