Boise is the capital and most populous city of the U.S. state of Idaho. It is the county seat of Ada County and the principal city of the Boise metropolitan area. It is the largest city between Salt Lake City, Utah and Portland, Oregon and thus serves as the primary government, economic, cultural, and transportation center for the area.

As of the 2006 Census Bureau estimates, Boise's population was 198,638, with a metropolitan area estimated to have 635,450 inhabitants, making it the most populous metropolitan area in Idaho.