the Jiyun (Chinese Ji2-yun4) is a Song dynasty revision of the Qieyun, the most important of the Chinese rime-books. It was completed in the second year of the Baoyuan reign period (1039) by a committee of officials led by Ding Du, after two years of work. The Guangyun had appeared only 30 years before, but was criticized for having done little to update the received contents of the book. The Jiyun is in 10 juan (10 Chinese volumes), a total of around 800 two-sided pages in traditional editions.

The Jiyun contains more characters than any other Chinese dictionary from traditional times - 53,525 of them, according to a recent source. Many of these are duplicates - characters that appear in more than one place because they have more than one pronunciation. Not only standard character forms are included - there are also large numbers of variants, as well as selected seal script forms and even some pre-Qin forms that had survived into the Song. Various other paleographical curiosities, such as the dozen or so strange forms promoted by Empress Wu, are included. For this reason, the Jiyun is particularly valuable for modern epigraphers.

The Jiyun is a revision of the Guangyun, which much more conservatively reflects the traditions of the original Qieyun. Although two years sounds like a short time in which to double the size of the Guangyun and transform its contents, in fact some of the changes are superficial. Many of the variant characters (though not the ancient forms) are already found in the Guangyun, where they are embedded in the text of the entries instead of being given their own full-size forms. The text of the Guangyun entries has been cut down substantially. numbers of other dictionaries seem to have been copied into the Jiyun - for instance, many xiaoyun end with a character bearing the "woman" classifier and the gloss "woman's name"; evidently all of these were taken from some now-lost dictionary of women's names. The name Jiyun means "collected rimes".

The phonological framework of the Jiyun is the same as that of its predecessors. But because so many xiaoyun have been added, the coherence of the fanqie have been lost as a tool for elucidating any sort of detailed phonological system. The fanqie have been (partially) revised, so that there is a much greater tendency for one sound to be represented by one element, and for all distinctions to be clearly made both upper and lower fanqie elements tend to be in the same tone category. This last revision seems to have been carried out mainly in the ping and shang tone categories, suggesting that it was abandoned half-way through.

At least two fully indexed reprints of Song editions were issued in the 1990's and remain widely reprinted.