Jia Dan (, 730 – 805), courtesy name Dunshi () and formally Duke Yuanjing of Wei (), was a Chinese cartographer, military general, and politician from Cangzhou, Hebei during the Tang dynasty. Background Jia Dan was born in 730, during the reign of Emperor Xuanzong. His family was from Cang Prefecture (滄州, in modern Cangzhou, Hebei) and traced its ancestry to the Han dynasty official Jia Yi, through officials of Cao Wei, Jin dynasty (266–420), Liu Song, Southern Qi, Liang dynasty, Northern Qi, Northern Zhou, Sui dynasty, and Tang dynasty. Both his grandfather Jia Zhiyi () and father Jia Yuanyan () served as county-level officials. Career Early career During Emperor Xuanzong's Tianbao era (742–756), Jia Dan passed the imperial examinations and was made the sheriff of Linqing County (臨清, in modern Liaocheng, Shandong). After he submitted suggestions on the matters of the times to Emperor Xuanzong, he was moved to be the sheriff of Zhengping County (正平, in modern Yuncheng, Shanxi) — closer to the capital Chang'an, and therefore considered a promotion despite it being the same level of office. While the general Wang Sili () served as the military governor (Jiedushi) of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi), Wang invited him to serve as secretary. While serving under Wang, Jia was promoted to be the deputy mayor of Taiyuan Municipality and deputy military governor. He later served as the prefect of Fen Prefecture (汾州, in modern Linfen, Shanxi) for seven years and was known for ruling the prefecture well. Jia was then recalled to Chang'an to serve as the minister of vassal affairs (鴻臚卿, Honglu Qing), which included the responsibilities of receiving and entertaining foreign emissaries, as well as imperial funerals and the command of two units of the imperial guards, the Weiyuan Camp (). As the minister of vassal affairs, he would have met with foreign envoys in order to acquire information about their native countries. This included cultural customs as well as geographic information, as a map was drawn after the geographic information was acquired from the interview. Historian Edward Schafer states that it is no doubt that Jia's remarkable knowledge of foreign geography was derived from these interviews with foreign delegates and diplomats. In 779, during the reign of Emperor Xuanzong's grandson Emperor Daizong, Jia was made the prefect of Liang Prefecture (梁州, in modern Hanzhong, Shaanxi) and the military governor of Shannan West