Cantonese (廣東話/广东话, lit. "Guangdong speech", colloquial; 粵語/粤语, lit. "Yuè dialect", formal) is one of the major dialects 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. Its name is derived from Canton, the former English name for Guangzhou, the capital city of Guangdong Province. It is a tonal language.

It is the lingua franca of the overseas Cantonese diaspora, spoken by about 70 million Cantonese worldwide. While fewer than the nearly one billion of Mandarin speakers, it is rivalled overseas only by the 40 million speakers of Hokkien, or Southern Fujianese dialects, many of whom are located throughout Southeast Asia. Cantonese is most commonly spoken in Hong Kong, a financial and cultural capital of southern China, and in one form or another in many if not most Chinatowns around the world with Cantonese communities. For instance, sei yap or siyi (四邑) dialect, from the 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.