Johnson County is a county located in the Eastern Coalfield of the U.S. state of Kentucky. As of the 2020 census, the population was 22,680. Its county seat is Paintsville. The county was formed in 1843 and named for Richard Mentor Johnson, a colonel of the War of 1812, United States Representative, Senator, and Vice President of the United States.

Johnson County is classified as a moist county, which is a county in which alcohol sales are not allowed (a dry county), but containing a "wet" city, in this case Paintsville, where alcoholic beverage sales are allowed.

Johnson County was formed on February 24, 1843, by the Kentucky General Assembly from land given by Floyd, Lawrence, and Morgan counties. At that time, its county seat of Paintsville had already been a chartered city for nine years. Homes had been built in Paintsville as early as the 1810s.

Many of the families at the beginning of Johnson County's formation were of Scottish, Irish, English, or German descent. Also, a fact lost to most historians is the large population of French Huguenots who were confused as English because they fled via England en route to the United States. Many of these settlers migrated from North Carolina, Pennsylvania, and Virginia following their participation in the Revolutionary War.

For about its first twenty-five years, Johnson County and Paintsville struggled along. Roads and highways were nonexistent. Mail and supplies reached Johnson County from the Bluegrass region by horseback and steamboat. Years later, stage coaches began to connect eastern Kentucky and Johnson County to the bluegrass region and the rest of civilization.

As Johnson County and its county seat had begun to thrive, in 1860 the Civil War became a disrupter. Like other border areas, brothers fought against brothers, tearing families apart. Johnson County was not only part of a border state during the Civil War, but it was a border county as well.

Sometime between 1860 and 1862, the county enacted an ordinance that neither the Union or Confederate flags were to be flown within the county. This was repealed quickly after Colonel James Garfield's Union brigade marched through Paintsville, (with the United States Flag being raised above the town courthouse) on its way to defeat the Confederate cavalry at the Battle of Middle Creek in Floyd County.

Following the Civil War, Thomas Jefferson Mayo moved to Paintsville to fulfill a role as a gifted and talented teacher. He fathered John C. C. Mayo, an important figure in the development of eastern Kentucky. The county citizenry is divided on their loyalty to his memory. Some^[who?] would say he was a benefactor who assisted in the development of Paintsville, and as a result, Johnson County. That he helped develop banks, churches, streets, public utilities and railroad transportation. Others^[who?] would say he was directly responsible for the huge influence coal companies had over the county's vast coal resources and the reason the region remains so economically depressed to this day.