Flat Gap (historically spelled Flatgap) is an unincorporated community in Johnson County, Kentucky, United States.

The community was named after the "flat gap" formed at the divide between the Lower Laurel and Mudlick Creeks.

Flat Gap's first post office was established on February 26, 1873, with Henry Jayne as postmaster.

[2] On June 2, 1990, one of the only tornadoes in Johnson County's history, touched down in Flat Gap at 1900.

The F1 tornado was 69 feet (23 yds) wide and created a one-mile (1.6 km) path of destruction.