Baixing (Chinese: 百姓; pinyin: bǎixìng; lit. 'hundred surnames') or lao baixing (Chinese: 老百姓; lit. 'old hundred surnames') is a traditional Chinese term, meaning "the people" or "commoners." The word "lao" (Chinese: 老; lit. 'old') is often added as a prefix before "baixing".

A confederation of tribes living along the Yellow River were the ancestors of what later became the Han ethnic group in China. Several large tribes, including the Huangdi tribes (Chinese: 黄帝族), Yandi tribes (Chinese: 炎帝族), and the Yi tribes, formed an alliance that consisted of roughly 100 tribes. This alliance is the origin of the Baixing, or the "hundred surnames."

Around 2,000 Han Chinese surnames are currently in use, but 19 of these surnames are used by about half of the Han Chinese people. About 87% of the population share 100 surnames.

Chinese family names are patrilineal, meaning derived from father to children. After marriage, Chinese women typically retain their maiden name. Two distinct types of Chinese surnames existed in ancient China: Namely xing (Chinese: 姓; pinyin: xìng) or ancestral clan names, and shi (Chinese: 氏; pinyin: shì) or branch lineage names. Later, the two terms began to be used interchangeably, and now xing refers to the surname, whereas shi may be used to refer to the clan name or maiden name. Historically, only Chinese men possessed xìng (Chinese: 姓; lit. 'family name'), while Chinese women had shì (Chinese: 氏; lit. 'clan') and took on their husband's xìng after marriage.

Hundred Family Surnames (Chinese: 百家姓), commonly known as Bai Jia Xing, is a classic Chinese text that lists Chinese surnames. The book was composed in the early Song dynasty. The text originally contained 411 surnames and was expanded to 504 over time.

In the dynasties following the Song, the Three Character Classic, the Hundred Family Surnames, and Thousand Character Classic came to be known collectively as San Bai Qian (Three, Hundred, Thousand), from the first word in their titles. San Bai Qian was the universal introductory literary text for students, almost exclusively males from elite backgrounds.

Chinese surnames have been proposed to be used as an alternative method of identifying an individual ethnicity. Secondary data sources used by health research may not include information on race or ethnicity, and surnames are often used as a proxy when researching health care in ethnic populations. A study published by BioMed Central (BMC), an open-access publisher of reliable peer-reviewed journals, asserts that surname lists help to identify cohorts of ethnic minority patients, and it attempted to validate the lists to identify people of South Asian and Chinese origin. The study in Ontario, Canada, reviewed lists of South Asian and Chinese surnames and compared these to the Registered Persons Directory to assign specific ethnicities. The findings were validated against self-identified ethnicity through responses to the Canadian Community Health Survey. The conclusion was that surname lists can identify cohorts with South Asian and Chinese origins with a high degree of accuracy.

A similar study in the Canadian Journal of Public Health on the validity of using surname to define Chinese ethnicity found that using surnames in existing health records and surname lists are reasonably sensitive and comparable.