Shanghainese (上海话 ), sometimes referred to as the Shanghai dialect, is a dialect of Wu Chinese spoken in the city of Shanghai. Shanghainese, like other Wu dialects, is not mutually intelligible with Standard Mandarin. Shanghainese is the representative dialect of Northern Wu; it contains vocabulary and expressions from the entire Northern Wu area (southern Jiangsu, northern Zhijiang). With nearly 14 million speakers, Shanghainese is also the largest single coherent form of Wu Chinese.

Shanghainese is rich in consonants and pure vowels. Like other northern Wu dialects, the Shanghai dialect has voiced initials, [b d g z v ] (although technically these are slack voiced, , adding a slightly breathy quality to a following vowel). Neither Mandarin nor Cantonese has voiced initials. The Shanghainese tonal system is significantly different from other Chinese languages. Shanghainese is a language with two live tonal contrasts (high and low), while Mandarin and Cantonese are contour tonal languages.

Though Shanghainese is commonly spoken among locals, it is not encouraged to be spoken in schools and written in newspapers, and the media are strongly discouraged from broadcasting in contemporary Shanghainese. Due to government fears of regionalism, thus most producers only produce in Mandarin. Several television advertisements in Shanghainese have been removed shortly after airing.

In August 2005, there were media coverages reporting that Shanghainese would be taught in secondary school. This introduced great controversy. Proponents argue that this will make the students know their hometown better and help preserve local culture. Opponents argue that this will encourage discrimination based on people's origin.

In September 2005, the Shanghai municipal government also launched a campaign to encourage Mandarin speaking in Shanghai. Among other requirements, all service-industry workers in Shanghai will be required to greet customers in Mandarin only, and pass Mandarin-fluency test by 2010. Those with bad or heavily-accented Mandarin must enroll in remedial Mandarin classes.