Cole County is located in the central part of the U.S. state of Missouri. As of the 2020 census, its population was 77,279. Its county seat and largest city is Jefferson City, the state capital. The county was organized November 16, 1820, and named after pioneer William Temple Cole who built Cole's Fort in Boonville.

Jefferson City, informally Jeff City, is the capital of the U.S. state of Missouri. It had a population of 43,228 at the 2020 census, ranking as the 15th most populous city in the state. It is also the county seat of Cole County and the principal city of the Jefferson City Metropolitan Statistical Area, the second-most-populous metropolitan area in Mid-Missouri and the fifth-largest in the state. Most of the city is in Cole County, with a small northern section extending into Callaway County. Jefferson City is named for Thomas Jefferson, the third President of the United States.