Letcher county is located in far southeastern Kentucky on the border with Virginia. It is a rugged, mountainous county and only Harlan county has higher elevations. Pine Mountain runs along the county line from the northeast to the southwest. The Pound Gap through Pine Mountain was an important passage for early settlers, and though most moved on, settlement in the area began around 1795. The county was formed in 1842 and named for Governor Robert P. Letcher. The county seat is Whitesburg. The population in 2010 was 24,519.

Coal mining has long been the principle industry in the county and several of its towns, including Jenkins, Fleming, and McRoberts, began as mining camps.

Letcher county was the setting for the early twentieth century novels The Little Shepherd of Kingdom Come and The Trail of the Lonesome Pine of John Fox, Jr. Kingdom Come State Park is located in the southwest of the county on the border with Harlan county. Lilley Cornett Woods, one of the largest tracts of protected old-growth forest in the state, is located in the county.