Shanghainese, a representative of the Wu dialect in China

Shanghainese, also known as the Shanghai or Hu dialect, is a form of Wu dialect spoken in the central districts of Shanghai and in the surrounding region. Wu speakers represented about 8% of the total Chinese population by 1984. Shanghainese is a proper representative dialect of Northern Wu and in English "Shanghainese" sometimes refers to all Wu dialects. With nearly 14 million speakers, it is also the largest single form of Wu Chinese. Shanghainese, like other Wu dialects, is largely unintelligible with other varieties of Chinese such as Mandarin.

Shanghai did not become a regional centre of commerce until it was opened to foreign investment during the late Qing dynasty. Consequently, dialects spoken around Shanghai had long been subordinate to those spoken around Jiaxing and later Suzhou. In the late 19th century, most vocabulary of the Shanghai region had been a hybrid between Northern Jiangsu and Ningbo dialects. Since the 1850s, owing to the growth of Shanghai's economy, Shanghainese has become one of the fastest-developing dialects of Wu Chinese, undergoing rapid changes and quickly replacing Suzhou dialect as the prestige dialect of the region. The sustained growth reached a hiatus in the 1930s during the Republican era, when migrants arrived in Shanghai and immersed themselves in the local tongue.

Shanghainese is rich in vowels and consonants. In particular, it has voiced initials. Neither Mandarin nor Cantonese has voiced initial stops or affricates. In terms of vowel quality inventory, the Jinhui dialect spoken in Shanghai's Fengxian District has 20 vowel qualities, the most among all world languages. The Shanghainese tonal system is also significantly different from other Chinese varieties. Shanghainese has two level tonal contrasts (high and low), while Mandarin and Cantonese are typical contour tonal languages.

Due to historical cultural effects, Shanghainese and Janpanese have some interesting intersections. The Shanghainese voiced consonants match the Japanese go-on readings nearly perfectly in terms of voicing. Some Shanghainese words' pronunciation can be expressed by Japanese hiragana, for example, "あつ", "らし", "しゃ" means "shoe", "rubbish", "write", respectively, in Shanghainese.

Shanghainese remained a very important part of the city's culture and retained its prestige status within the local population. Due to the national prominence of Mandarin, from 1992 Shanghainese was discouraged in schools, and many children no longer speak Shanghainese. However, from 2005, new compaign emerged to call for the preservation and documentation of Shanghainese. At municipal legislative discussions in 2005, former Shanghai opera actress Ma Lili moved to "protect" the dialect, stating that she was one of the few remaining Shanghai opera actresses who still retained authentic classic Shanghainese pronunciation in their performances. Nowadays, more TV programs are appearing in Shanghainese as well as other Wu varieties. Popular video websites in China, such as Youku and Tudou, also host a variety of user-uploaded audio and visual media in many Wu dialects, most of which are dialectal TV shows for entertainment.

Tianxing He and Kai Yu are with the Computer Science and Engineering Department, Shanghai Jiao Tong University.