Sanhe is a county-level city administered by the Langfang prefecture-level city in eastern Hebei province, People's Republic of China. Sanhe city, Dachang Hui Autonomous County, and Xianghe County form the "Northern Three Counties of Langfang", an exclave of Hebei province surrounded by the Beijing and Tianjin municipalities.

Langfang is a prefecture-level city of Hebei Province, and was known as Tianjin Prefecture until 1973. It was renamed Langfang Prefecture after Tianjin became a municipality and finally upgraded into a prefecture-level city in 1988. Langfang is located approximately midway between Beijing and Tianjin. At the 2020 census, the population of Langfang was 5,464,087, of whom 1,147,591 lived in the built-up area made of Guangyang and Anci districts; its total area is around 6,417.28 km2 (2,477.73 sq mi). Langfang borders Baoding to the southwest, Cangzhou to the south, Beijing to the north and Tianjin to the east. Sanhe City and Dachang Hui County are now conurbated with Beijing, so that they form part of the same built-up area. Langfang is the smallest prefecture-level city of Hebei Province by land area.