Hongtong county is located in the southern part of Shanxi province, at the northern end of the Linfen Basin. To the east, it neighbors Guxian county across Huoshan Mountain; to the west, it borders Puxian county via Lyuliang city. It adjoins Huozhou and Fenxi counties to the north and Yaodu district to the south.

Hongtong derives its name from "Hongya" in the south and "Gudong" in the north. During the Western Zhou Dynasty (c.11th century-771 BC), it was known as Yanghou State. After the six kingdoms were unified and the prefecture-county system was implemented during the Qin Dynasty (221-206 BC), Hongtong became Yangxian county. In the second year of the Yining era of the Sui Dynasty (581-618), Yangxian county was renamed Hongtong county, and this name has been used ever since.

Hongtong governs 15 towns and townships and 325 villages, with a permanent population of 637,000, making it the most populous county in Shanxi province. It spans a total area of 1,494 square kilometers. The county has 210 frost-free days annually, an average temperature of 12.7 C, 2,079.1 hours of sunshine per year, and an average annual precipitation of 441.5 millimeters. Hongtong's average elevation is 430 meters, while its highest point, Huoshan Mountain's Laoye Peak, stands at 2,347 meters above sea level.

Hongtong has 1.02 million mu (68,000 hectares) of arable land, evenly split between irrigated and dry fields. The main crops are wheat and corn, supplemented by beans, potatoes, and minor grains. With its single and multi-season planting cycles, the county serves as a national commercial grain production base and a provincial high-quality wheat production base.