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 歐 is listed 361st in the Song dynasty classic text Hundred Family Surnames.[1] As of 2008, Ou 欧 is the 134th most common surname in China, shared by 1.13 million people.[2]
Most recently, by using the 2010 China census data and statistical analysis data that included random sampling from Taiwan, Hong Kong and Macau, the Fuxi Culture Research Association ranked the surname 区/區 291st most common in China, shared by around 199,000 people (0.015% of the Chinese population) with the largest concentration of holders in Guangdong province.[3]