Taishanese (simplified Chinese: 台山话; traditional Chinese: 臺山話; pinyin: Táishān huà; Jyutping: toi4 saan1 waa2), alternatively romanized in Cantonese as Toishanese or Toisanese, in local dialect as Hoisanese or Hoisanwa, is a Yue Chinese language native to Taishan, Guangdong.

Even though they are related, Taishanese has little mutual intelligibility with Cantonese. It is not a dialect of Cantonese. Taishanese is also spoken throughout Sze Yup (or Siyi in the pinyin romanization of Standard Mandarin Chinese), located on the western fringe of the Pearl River Delta in Guangdong, China. In the late 19th century and early 20th century, most of the Chinese emigration to North America originated in Sze Yup (which includes Taishan). Thus, up to the mid-20th century, Taishanese was the dominant variety of the Chinese language spoken in Chinatowns in Canada and the United States. It was formerly the lingua franca of the overseas Chinese residing in the United States.

The earliest linguistic studies refer to the dialect of Llin-nen or Xinning (traditional Chinese: 新寧; simplified Chinese: 新宁). Xinning was renamed Taishan in 1914, and linguistic literature has since generally referred to the local dialect as the Taishan dialect, a term based on the pinyin romanization of Standard Mandarin Chinese pronunciation. Alternative names have also been used. The term Toishan is a convention used by the United States Postal Service, the Defense Language Institute and the 2000 United States census. The terms Toishan, Toisan, and Toisaan are all based on Cantonese pronunciation and are also frequently found in linguistic and non-linguistic literature. Hoisan is a term based on the local pronunciation, although it is not generally used in published literature.

These terms have also been anglicized with the suffix -ese: Taishanese, Toishanese, and Toisanese. Of the previous three terms, Taishanese is most commonly used in academic literature, to about the same extent as the term Taishan dialect. The terms Hoisanese and Hoisan-wa do appear in print literature, although they are used more on the internet.

Another term used is Sìyì (Sze Yup or Seiyap in Cantonese romanization; Chinese: 四邑; lit. 'four counties'). Sìyì or Sze Yup refers to a previous administrative division in the Pearl River Delta consisting of the four counties of Taishan, Kaiping, Enping and Xinhui. In 1983, a fifth county (Heshan) was added to the Jiangmen prefecture; so whereas the term Sìyì has become an anachronism, the older term Sze Yup remains in current use in overseas Chinese communities where it is their ancestral home. The term Wǔyì (Chinese: 五邑), literally "five counties", refers to the modern administrative region, but this term is not used to refer to Taishanese.

Taishanese originates in the Taishan region, where it is spoken. Taishanese can also be seen as a group of very closely related, mutually intelligible dialects spoken in the various towns and villages in and around the Siyi region (literally the 'Four Counties' of Toishan, Hoiping, Yanping, Sunwui, transcribed from Standard Cantonese; the names Taishan, Kaiping, Enping and Xinhui, as above, are romanized from Standard Mandarin using Pinyin).

Although this area started undergoing sinicization from the late Han dynasty, Xinhui was decreed as a district during the Northern and Southern dynasties, whilst Enping was established in 622 during the Tang dynasty. Taishan itself was split from Xinhui in 1499, during the Ming dynasty, whilst Kaiping was established in 1649 during the Qing dynasty from territory formerly under Xinhui, Enping, and Xinxing. Thus, as a branch of Yue Chinese, Taishanese is derived from Middle Chinese. Within Siyi, Taishanese proper is closest to the dialect of Kaiping, both phonologically and lexically. It also bears phonological resemblance to the speech of Heshan, a later addition to the region.

A vast number of Taishanese immigrants journeyed worldwide through the Taishan diaspora. The Taishan region was a major source of Chinese immigrants through continental Americas from the late-19th to mid-20th centuries. Taishanese was the predominant dialect spoken by the 19th-century Chinese builders of railroads in North America. Approximately 1.3 million people are estimated to have origins in Taishan. Prior to the signing of the Immigration and Naturalization Act of 1965, which allowed new waves of Chinese immigrants, Taishanese was the dominant dialect spoken in Chinatowns across North America.