CaO

Cao is a Chinese surname written 曹. It is one of the more common Chinese surnames and is borne by people across China and in overseas Chinese communities. The surname has multiple origins, with the most widely cited tracing to the feudal state of Cao (曹国) during the Zhou dynasty; descendants of the ruling family adopted the place name as their surname. Over time, the Cao lineage spread through migration and intermarriage, becoming established in many regions.

In terms of distribution, Cao is found throughout China and among global Chinese communities, including Southeast Asia, North America, and Europe. The surname has several romanizations depending on dialect and historical transcription, including Cao (Mandarin pinyin) and Tsao or Tsau in older or non-Mardarin contexts.

Notable individuals with the surname include Cao Cao (155–220), a prominent warlord and Chancellor during the late Eastern Han who laid the foundations for the state of Cao Wei; his son Cao Pi (187–226), who established Wei as its first emperor; Cao Zhi (192–232), a celebrated poet and brother of Pi; and Cao Xueqin (1715–1763), the author of Dream of the Red Chamber, regarded as one of China's greatest novels.

Beyond the surname, the syllable cao occurs in many Chinese words, such as 草 (grass), and appears in various names and place names. The name Cao thus functions as an enduring element in Chinese genealogies and identity, carried by many generations and communities.