Kanbun (漢文 'Han writing') is a system for writing Literary Chinese used in Japan from the Nara period until the 20th century. Much of Japanese literature was written in this style and it was the general writing style for official and intellectual works throughout the period. As a result, Sino-Japanese vocabulary makes up a large portion of the Japanese lexicon and much classical Chinese literature is accessible to Japanese readers in some resemblance of the original.

Kanbun in its most literal definition means "Chinese writing". The Japanese writing system originated through adoption and adaptation of written Chinese (kanbun). Some of Japan's oldest books (e.g. the Nihon Shoki) and dictionaries (e.g. the Tenrei Banshō Meigi and Wamyō Ruijushō) were written in kanbun. Other Japanese literary genres have parallels; the Kaifūsō is the oldest collection of kanshi (漢詩; 'Chinese poetry'). Burton Watson's English translations of kanbun compositions provide an introduction to this literary field.

Kanbun is described by Jean-Noël Robert as a "perfectly frozen 'dead'" language that was continuously used from the late Heian period (794–1185) until after World War II. Kanbun, otherwise known as Classical Chinese or Literary Chinese, had long since ceased to be a colloquial language in China. Yet all the oldest writing in Japan are in kanbun and predate any written documents in Japanese, although there is considerable debate if these Chinese texts contained traces of the Japanese vernacular. Taking into consideration all the texts written in both Japanese and Chinese, including monastic documents, as well as 'near-Chinese' (hentai-kanbun) texts, the amount of Chinese writing in Japan may exceed what was written in Japanese. Despite the size, quality, and importance of kanbun writing, John Timothy Wixted notes that scholars have disregarded kanbun as an area of study until recent times and it is the least properly represented part of the Japanese canon.

Aside from Chinese writing, kanbun also refers to a genre of techniques for reading Chinese texts read like Japanese or for writing in a way similar to Chinese. Samuel Martin coined the term Sino-Xenic in 1953 to describe Chinese as written in Japan, Korea, and other foreign (hence -xenic) zones on China's periphery. Roy Andrew Miller notes that although Japanese kanbun conventions have Sino-Xenic parallels with other traditions for reading Literary Chinese like Korean hanmun and Vietnamese Hán Văn, only kanbun has survived to the present day.

In the Japanese kanbun reading tradition, the Chinese text is transformed through punctuation, analysis, and translation into classical Japanese. Through a limited canon of Japanese forms and syntactic structures treated as though they existed in alignment with vocabulary and structures of Classical Chinese, the kanbun text could be read in drastically different ways. At its most extreme, this type of reading could render the text so simplified that it could be understood through an elementary student's perspective. At its best, it could preserve a large body of Classical Chinese texts that would have otherwise been lost. Thus the kanbun could also be of great value for understanding early Chinese literature.

There were several linguistic hurdles involved in kanbun transformation. Chinese grammatical order is subject–verb–object (SVO) and uses particles similar to English prepositions whereas morphemes are typically one syllable in length and inflection plays no role in the grammar. Conversely, Japanese sentence order uses SOV with syntactic features, including post positions such as grammar particles that appear after the words and phrases to which they apply.

Four major problems faced when transforming kanbun are the word order, parsing which Chinese characters should be read together, deciding how to pronounce the characters, and finding suitable equivalents for Chinese function words.

A new development in kanbun studies is the Web-accessible database being developed by scholars at Nishogakusha University in Tokyo.^{[clarification needed]}