Mandarin ( 北方方言 ), is a category of related Chinese dialects spoken across most of northern and southwestern China. Mandarin can also refer to Standard Mandarin, which is based on the Mandarin dialect spoken in Beijing. Standard Mandarin is the official spoken language of the People's Republic of China—where it is known as Putonghua ( 普通话; literally, "the common tongue" ). It is also one of the official spoken languages of Singapore. When taken as an independent language, as is often done in academic literature, Mandarin has more speakers than any other language. "Chinese"—de facto, Mandarin—is one of the six official languages of the United Nations.

"Mandarin" usually refers to only standard Mandarin in everyday usage. The broad academic concept of "Mandarin" encompasses a large number of linguistically related dialects, some less mutually intelligible than others, and is very rarely used outside of academic circles as a self-description. Instead, when asked to describe the spoken form they are using, Chinese speaking a form of Mandarin will describe the variant that they are speaking, for example Sichuan dialect or Northeast China dialect, and may not recognize that it is in fact classified by linguists as a form of "Mandarin". Nor is there a common "Mandarin" identity based on language—due to the wide geographical distribution of speakers—though there are strong regional identities centered around individual Mandarin dialects.

The present main divisions of the Chinese language developed out of Old Chinese and Middle Chinese.

Most Chinese living in a broad arc, from the north-east (Manchuria) to the south-west (Yunnan), use various Mandarin dialects as their home language. The prevalence of linguistic homogeneity (i.e. Mandarin) throughout northern China is largely the result of geography, namely the plains of north China. By contrast, the mountains and rivers of southern China have promoted linguistic diversity. The presence of Mandarin in southwest China is largely due to a plague in the 12th century in Sichuan. This plague, which may have been related to the black death, depopulated the area, leading to later settlement from north China.

There is no clear dividing line where Middle Chinese ends and Mandarin begins; however, the Zhongyuan Yinyun (中原音韵), a rhyme book from the Yuan Dynasty, is widely regarded as an important milestone in the history of Mandarin. In this rhyme book we see many characteristic features of Mandarin, such as the reduction and disappearance of final stop consonants and the reorganization of the Middle Chinese tones.

Until the mid-20th century, most Chinese living in southern China did not speak any Mandarin. However, despite the mix of officials and commoners speaking various Chinese dialects, Beijingese Mandarin became dominant at least during the officially Manchu-speaking Qing Empire. Since the 17th century, the Empire had set up Orthoepy Academies ( 正音书院 Zhengyin Shuyuan ) in an attempt to make pronunciation conform to the Beijing standard. But these attempts had little success.

This situation changed with the creation of an elementary school education system committed to teaching Mandarin. As a result, Mandarin is now spoken fluently by most people in Mainland China and in Taiwan. In Hong Kong, the language of education and formal speech remains Cantonese but Mandarin is becoming increasingly influential.