Cantonese (traditional Chinese: 廣東話; simplified Chinese: 广东话; Jyutping: Gwong2 dung1 waa2; Cantonese Yale: Gwóngdūng wá) is a language within the Chinese (Sinitic) branch of the Sino-Tibetan languages originating from the city of Guangzhou (historically known as Canton) and its surrounding area in Southeastern China. It is the traditional prestige variety of the Yue Chinese group, which has over 82.4 million native speakers. While the term Cantonese specifically refers to the prestige variety, it is often used to refer to the entire Yue (粤) subgroup of Chinese, including related but largely mutually unintelligible languages and dialects such as Taishanese.

Cantonese is viewed as a vital and inseparable part of the cultural identity for its native speakers across large swaths of Southeastern China, Hong Kong and Macau, as well as in overseas communities. In mainland China, it is the lingua franca of the province of Guangdong (being the majority language of the Pearl River Delta) and neighbouring areas such as Guangxi. It is also the dominant and co-official language of Hong Kong and Macau. Cantonese is also widely spoken amongst Overseas Chinese in Southeast Asia (most notably in Vietnam and Malaysia, as well as in Singapore and Cambodia to a lesser extent) and throughout the Western world.

Although Cantonese shares much vocabulary with Mandarin, the two Sinitic languages are mutually unintelligible, largely because of phonological differences, but also due to the differences in grammar and vocabulary. Sentence structure, in particular the placement of verbs, sometimes differs between the two varieties. A notable difference between Cantonese and Mandarin is how the spoken word is written; both can be recorded verbatim, but very few Cantonese speakers are knowledgeable in the full Cantonese written vocabulary, so a non-verbatim formalized written form is adopted, which is more akin to the Mandarin written form or Standard Chinese. However, it is only non-verbatim with respect to vernacular Cantonese as it is possible to read Standard Chinese text verbatim with formal Cantonese. This results in the situation in which a Cantonese and a Mandarin text may look similar but are pronounced differently. Conversely, written (vernacular) Cantonese is mostly used in informal settings such as on social media and comic books.