Jefferson County may refer to the following counties in the United States:

Jefferson County, Alabama

Jefferson County, Arkansas

Jefferson County, Colorado

Jefferson County, Jefferson Territory

Jefferson County, Florida

Jefferson County, Georgia

Jefferson County, Idaho

Jefferson County, Illinois

Jefferson County, Indiana

Jefferson County, Iowa

Jefferson County, Kansas

Jefferson County, Kentucky

Jefferson County, Mississippi

Jefferson County, Missouri

Jefferson County, Montana

Jefferson County, Nebraska

Jefferson County, New York

Jefferson County, Ohio

Jefferson County, Oklahoma

Jefferson County, Oregon

Jefferson County, Pennsylvania

Jefferson County, Tennessee

Jefferson County, Texas

Jefferson County, Virginia, has existed twice; the two counties continue in existence as Jefferson County, Kentucky and Jefferson County, West Virginia

Jefferson County, Washington

Jefferson County, West Virginia

Jefferson County, Wisconsin