A rime dictionary, rhyme dictionary, or rime book (traditional Chinese: 韻書; simplified Chinese: 韵书; pinyin: yùnshū) is a genre of dictionary that records pronunciations for Chinese characters by tone and rhyme, instead of by graphical means like their radicals. The most important rime dictionary tradition began with the Qieyun (601), which codified correct pronunciations for reading the classics and writing poetry by combining the reading traditions of north and south China. This work became very popular during the Tang dynasty, and went through a series of revisions and expansions, of which the most famous is the Guangyun (1007–1008).

These dictionaries specify the pronunciations of characters using the fanqie method, giving a pair of characters indicating the onset and remainder of the syllable respectively. The later rime tables gave a significantly more precise and systematic account of the sounds of these dictionaries by tabulating syllables by their onsets, rhyme groups, tones and other properties. The phonological system inferred from these books, often interpreted using the rime tables, is known as Middle Chinese, and has been the key datum for efforts to recover the sounds of early forms of Chinese. It incorporates most of the distinctions found in modern varieties of Chinese, as well as some that are no longer distinguished. It has also been used together with other evidence in the reconstructions of Old Chinese.

Some scholars use the French spelling rime, as used by the Swedish linguist Bernard Karlgren, for the categories described in these works, to distinguish them from the concept of poetic rhyme.

Chinese scholars produced dictionaries to codify reading pronunciations for the correct recitation of the classics and the associated rhyme conventions of regulated verse. The earliest rime dictionary was the Shenglei (lit. 'sound types') by Li Deng (李登) of the Three Kingdoms period, containing more than 11,000 characters grouped under the five notes of the ancient Chinese musical scale. The book did not survive, and is known only from descriptions in later works.

Various schools of the Jin dynasty and Northern and Southern dynasties produced their own dictionaries, which differed on many points. The most prestigious standards were those of the northern capital Luoyang and the southern capital Jinling (modern Nanjing). In 601, Lu Fayan (陸法言) published his Qieyun, an attempt to merge the distinctions in five earlier dictionaries. According to Lu Fayan's preface, the initial plan of the work was drawn up 20 years earlier in consultation with a group of scholars, three from southern China and five from the north. However the final compilation was by Lu alone, after he had retired from government service.

The Qieyun quickly became popular as the standard of cultivated pronunciation during the Tang dynasty. The dictionaries on which it was based fell out of use, and are no longer extant. Several revisions appeared, of which the most important were:

In 1008, during the Song dynasty, a group of scholars commissioned by the emperor produced an expanded revision called the Guangyun. The Jiyun (1037) was a greatly expanded revision of the Guangyun. Lu's initial work was primarily a guide to pronunciation, with very brief glosses, but later editions included expanded definitions, making them useful as dictionaries.

Until the mid-20th century, the oldest complete rime dictionaries known were the Guangyun and Jiyun, though extant copies of the latter were marred by numerous transcription errors. Thus all studies of the Qieyun tradition were actually based on the Guangyun. Fragments of earlier revisions of the Qieyun were found early in the century among the Dunhuang manuscripts, in Turfan and in Beijing.