Hong is the pinyin romanization of the Chinese surname 洪 (Hóng). It was listed 184th among the Song-era Hundred Family Surnames. Today it is not among the 100 most common surnames in mainland China but it was the 15th-most-common surname in Taiwan in 2005. As counted by a Chinese census, Taiwan is the area with the largest number of people with the name. It is also the pinyin romanization of a number of less-common names including Hóng (弘), Hóng (t 閎, s 闳), and Hóng (宏). All of those names are romanized as Hung in Wade-Giles.

"Hong" is also one spelling employed for the Cantonese pronunciation of the surname Xiong (熊).

The Hokkien and Teochew romanization of Hong (that uses the character 洪) is Ang, which is also used for Wang (汪, Wāng).

It is also the romanization used for the Korean surname Hong, which uses the character 洪 in hanja, the Khmer surname ហុង (Hong), as well as the surname Hồng in Vietnam, from the Sino-Vietnamese reading of Chinese character 洪.

This section does not cite any sources. (March 2012)

The name 洪 literally means "flood".

The legendary origin of the family links it to descendants of the Yan Emperor who originally bore the ancestral name (xing) Jiang (姜) and the clan name "Gonggong" (共工). The Gonggongs directed irrigation works and managed flood control on the west bank of the Yellow River in the southeast corner of the Ordos Loop above the Wei.

After the Yellow Emperor conquered the Yan Emperor's territory, his relatives and descendants were persecuted and the Gonggong rebelled during the reign of the Gaoyang Emperor. The future Ku Emperor led an army against the rebellion and crushed them at the Battle of Bei Zhou Shan. Supposedly, among his soldiers were the descendants of Suiren, credited with the invention of fire, so that this is referred to in Chinese sources as a battle between fire and water. The Gonggong were reinstated in their former position only to provoke widespread flooding under the Yao Emperor when they opposed some of his orders. A second army brought a second defeat and the Yao Emperor banished the Gonggong to Jiangnan.

When the Chinese ceased to have both ancestral and clan names, many Gonggongs combined the water radical from jiang with the character gong to produce Hong.^{[dubious – discuss]}

Dunhuang in Gansu and Nanchang in Jiangxi.^{[citation needed]}