Cantonese ( 粤语 ) is one of the major dialect groups or languages of the Chinese language or language family. It is mainly spoken in the south-eastern part of Mainland China, Hong Kong, Macau, by the Chinese minorities in Southeast Asia and by many overseas Chinese of Cantonese origin worldwide. The name is derived from Canton, a former romanized Western name for Guangzhou ( 广州 ), the capital of Guangdong ( 广东 ) province.

Different dialects of Cantonese are spoken depending on area. The most prestigious is the Guangzhou dialect, also referred to simply as "Cantonese". The Guangzhou dialect is the lingua franca of not just Guangdong province, but also the overseas Cantonese diaspora, spoken by about 70 million Cantonese worldwide. The Guangzhou dialect is also spoken in Hong Kong, a financial and cultural capital of southern China. In addition to the Guangzhou dialect, the Taishan dialect, one of the sei yap or siyi ( 四邑 ) dialects that come from Guangdong counties where a majority of Exclusion-era Cantonese-Chinese immigrants emigrated, continues to be spoken both by recent immigrants from Southern China and even by third-generation Chinese Americans of Cantonese ancestry alike.

Like other major varieties of Chinese, Cantonese is often considered a dialect of a single Chinese Language for cultural or nationalistic reasons; most linguists consider Cantonese a separate language in the sense that they use the term, with notable exceptions in the People's Republic of China.

There are at least four major dialect groups of Cantonese: Yuehai, which includes the dialect spoken in Guangzhou, Hong Kong and Macau as well as the dialects of Zhongshan ( 中山 ), and Dongguan ( 东莞 ); Siyi ( 四邑 ), exemplified by Taishan  ( 台山 ) dialect, which used to be ubiquitous in American Chinatowns before 1970; Gaoyang ( 高阳 ), as spoken in Yangjiang ( 阳江 )  ; and Guinan ( 桂南 ) spoken widely in Guangxi. However, Cantonese generally refers to the Yuehai dialect.

For the last 150 years, Guangdong Province has been the home of most of the Chinese emigrants; one county near its center, Taishan, alone may have been the home to more than 60% of Chinese immigrants to the US before 1965, and as a result, Guangdong dialects such as sei yap (the dialects of Taishan 台山, Enping 恩平, Kaiping 开平, Xinhui 新会 Counties) and what we understand to be mainstream Cantonese (with a heavy Hong Kong influence) have been the major spoken dialects abroad. As more and different kinds of Chinese emigrate, however, the situation is now changing, so that Min (Hokkien, or Fujianese dialect speakers) and Wu dialect speakers are also now heard, as well as Mandarin in increasing numbers from Taiwanese and Northern mainland immigrants.

In addition, there are at least three other major Chinese languages spoken in Guangdong Province—Putonghua 普通话, which is official standard Mandarin, spoken in official occasions, used in education, and among the many internal migrants from the north seeking work in the developing south; Min-nan 闽南 (Southern Min) spoken in the eastern regions bordering Fújiàn 福建, such as those from Chaozhou 潮州 and Shantou 汕头; and Hakka 客家(话), the language of the Hakka minority 客家(人). Hanyu 汉语 or Mandarin is mandatory through the state education system, but in the Southern household, the popularization of Cantonese-language media, isolation from the other regions of China, and the healthy economy of the Cantonese diaspora ensure that the language has a life of its own. Most wuxia films from Canton are filmed originally in Cantonese and then dubbed in Mandarin or English or both.