Written Chinese is a writing system that uses Chinese characters and other symbols to represent the Chinese languages. Chinese characters do not directly represent pronunciation, unlike letters in an alphabet or syllabograms in a syllabary. Rather, the writing system is morphosyllabic: characters are one spoken syllable in length, but generally correspond to morphemes in the language, which may either be independent words, or part of a polysyllabic word. Most characters are constructed from smaller components that may reflect the character's meaning or pronunciation. Literacy requires the memorization of thousands of characters; college-educated Chinese speakers know approximately 4,000. This has led in part to the adoption of complementary transliteration systems (generally Pinyin) as a means of representing the pronunciation of Chinese.

Chinese writing is first attested during the late Shang dynasty (c. 1250 – c. 1050 BCE), but the process of creating characters is thought to have begun centuries earlier during the Late Neolithic and early Bronze Age (c. 2500–2000 BCE). After a period of variation and evolution, Chinese characters were standardized under the Qin dynasty (221–206 BCE). Over the millennia, these characters have evolved into well-developed styles of Chinese calligraphy. As the varieties of Chinese diverged, a situation of diglossia developed, with speakers of mutually unintelligible varieties able to communicate through writing using Literary Chinese. In the early 20th century, Literary Chinese was replaced in large part with written vernacular Chinese, largely corresponding to Standard Chinese, a form based on the Beijing dialect of Mandarin. Although most other varieties of Chinese are not written, there are traditions of written Cantonese, written Shanghainese and written Hokkien, among others.

Written Chinese is not based on an alphabet or syllabary. Most characters can be analyzed as compounds of smaller components, which may be assembled according to several different principles. Characters and components may reflect aspects of meaning or pronunciation. The best known exposition of Chinese character composition is the Shuowen Jiezi, compiled by Xu Shen c. 100 CE. Xu did not have access to the earliest forms of Chinese characters, and his analysis is not considered to fully capture the nature of the writing system. Nevertheless, no later work has supplanted the Shuowen Jiezi in terms of breadth, and it is still relevant to etymological research today.

According to the Shuowen Jiezi, Chinese characters are developed on six basic principles. (These principles, though popularized by the Shuowen Jiezi, were developed earlier; the oldest known mention of them is in the Rites of Zhou, a text from c. 150 BCE.) The first two principles produce simple characters, known as 文 (wén):

The remaining four principles produce complex characters historically called 字 (zì), though this term is now generally used to refer to all characters, whether simple or complex. Of these four, two construct characters from simpler parts:

The last two principles do not produce new written forms; they instead transfer new meanings to existing forms:

In contrast to the popular conception of written Chinese as ideographic, the vast majority of characters—about 95% of those in the Shuowen Jiezi—either reflect elements of pronunciation, or are logical aggregates. In fact, some phonetic complexes were originally simple pictographs that were later augmented by the addition of a semantic root. An example is 炷; zhù; 'lampwick', now archaic, which was originally a pictograph of a lamp stand 主, a character that is now pronounced zhǔ and means 'host', or the character 火 (huǒ; 'fire') was added to indicate that the meaning is fire related.

Chinese characters are written to fit into a square, even when composed of two simpler forms written side-by-side or top-to-bottom. In such cases, each form is compressed to fit the entire character into a square.