Yongchang County (Chinese: 永昌县; pinyin: Yǒngchāng Xiàn) is a county located in the southern half of the prefecture-level city of Jinchang in north-central Gansu province, China, bordering Qinghai to the south.

The village of Zhelaizhai, located in Jiaojiazhuang township, has been the subject of international academic and media attention for its potential connection to Sino-Roman relations.

The ancient Northern Silk Road passes through Yongchang County; numerous Han envoys were sent west along this trackway, some parties exceeding 100 members, late in the first millennium BC.

The Han dynasty sent one mission to Parthia, which was reciprocated around 100 BC: Roman emissaries were captured by the Chinese in 30 BC along the Silk Road at Yongchang.

[2] At various times during the 20th century and early 21st century, the county has entered the sight of media because some of the inhabitants of Jiaojiazhuang township's Liqian village (骊靬村) (Zhelaizhai), located where the ancient Liqian county had existed in the early imperial period (Western Han dynasty to Sui dynasty), have been theorized to be descendants of a Roman legion.