Marion County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 9,725. Its county seat is Jefferson. Marion County is in East Texas and is named for Francis Marion, the Revolutionary War general from South Carolina who was nicknamed the "Swamp Fox".

East Texas is a broadly defined cultural, geographic, and ecological region in the eastern part of the U.S. state of Texas that comprises most of 41 counties. It is primarily divided into Northeast and Southeast Texas. Most of the region consists of the Piney Woods ecoregion. East Texas can sometimes be defined only as the Piney Woods. At the fringes, towards Central Texas, the forests expand outward toward sparser trees and eventually into open plains.