Shanghainese (上海閒話 [z̥ɑ̃̀héɦɛ̀ɦʊ̀] in Shanghainese), or the Shanghai language (simplified Chinese: 上海话 or 沪语; traditional Chinese: 上海話 or 滬語), is a dialect of Wu Chinese spoken in the city of Shanghai and the surrounding region. It is classified as part of the Sino-Tibetan family of languages. Shanghainese, like other Wu dialects, is largely not mutually intelligible with other Chinese varieties such as Mandarin. The term "Shanghainese" in English sometimes refers to all Wu Chinese dialects, though it is only partially intelligible with some other subbranches of the Wu language group.

Shanghainese is a representative dialect of Northern Wu; it contains vocabulary and expressions from the entire Northern Wu area (southern Jiangsu, northern Zhejiang). With nearly 14 million speakers, Shanghainese is also the largest single coherent form of Wu Chinese. It once served as the regional lingua franca of the entire Yangtze River Delta region.

Shanghainese is rich in consonants and pure vowels [i y ɪ e ø ɛ ə ɐ a ɑ ɔ ɤ o ʊ u] (of which 8 are phonemic). Like other northern Wu dialects, the Shanghai dialect has voiced initials [b d ɡ ɦ z v dʑ ʑ]. Neither Mandarin nor Cantonese has voiced stops or affricates. 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.