Ou is the pinyin romanization of the Chinese surnames 區 and 歐, which share a common origin with the compound surname Ouyang (歐陽), from the ruling family of the State of Yue during the Spring and Autumn period. They are commonly romanized as Au or Ao in Cantonese.
Ou was the 27,293th most common surname in the United States during the 1990 census and the 11,845th most common surname during the 2000 census. Au ranked 11,417th and 5,195th, and Ao ranked 88,459th and 58,402nd.
List of persons with the surname
- "百家姓" [Hundred Family Surnames] (in Chinese). Guoxue. Retrieved 2014-10-28.
- 中国最新300大姓排名（2008） [300 most common surnames in China (2008)] (in Chinese). Taiwan.cn. 2009-01-06. Retrieved 2014-10-28.
- US Census Bureau. Op. cit. Public Broadcasting Service. "How Popular Is Your Last Name?" Accessed 6 Apr 2012.