The French post office in Hai-Hao operated from around 1900 to 1904, located in southern China near the border with French Indochina. Though not a formal colony, the area was under significant French commercial and military influence, serving as a frontier post linked to the broader Indochinese network. French stamps overprinted "CHINE" were used, and postmarks with spellings like Hai-Hao, Haihao, and Hai-Hau appear on surviving mail. The post office reflects France’s semi-colonial presence in the region, tied to trade, rail expansion, and geopolitical strategy in southern China.