Jin (simplified Chinese: 晋语; traditional Chinese: 晉語; pinyin: Jìnyǔ) is a group of Chinese linguistic varieties spoken by roughly 48 million people in northern China, including most of Shanxi province, much of central Inner Mongolia, and adjoining areas in Hebei, Henan, and Shaanxi provinces. The status of Jin is disputed among linguists; some prefer to include it within Mandarin, but others set it apart as a closely related but separate sister group.

After the concept of Mandarin Chinese was proposed, the Jin dialects were universally included within it, mainly because Chinese linguists paid little attention to these dialects at the time. In order to promote Standard Mandarin in the early days of People's Republic of China, linguists started to research various dialects in Shanxi, comparing these dialects with Standard Mandarin for helping the locals to learn it more quickly. During this period, a few linguists discovered some unique features of Jin Chinese that do not exist in other northern Mandarin dialects, planting the seeds for the future independence of Jin Chinese. Finally, in 1985, Li Rong proposed that Jin should be considered a separate top-level dialect group, similar to Yue or Wu. His main criterion was that Jin dialects had preserved the entering tone as a separate category, still marked with a glottal stop as in the Wu dialects, but distinct in this respect from most other Mandarin dialects. Some linguists have adopted this classification. However, others disagree that Jin should be considered a separate dialect group for these reasons:

The Language Atlas of China divides Jin into the following eight groups:

The Taiyuan dialect from the Bingzhou group is sometimes taken as a convenient representative of Jin because many studies of this dialect are available, but most linguists agree that the Taiyuan vocabulary is heavily influenced by Mandarin, making it unrepresentative of Jin. The Lüliang group is usually regarded as the "core" of the Jin language group as it preserves most archaic features of Jin. However, there is no consensus as to which dialect among the Lüliang group is the representative dialect.

Unlike most varieties of Mandarin, Jin has preserved a final glottal stop, which is the remnant of a final stop consonant (/p/, /t/ or /k/). This is in common with the Early Mandarin of the Yuan dynasty (c. 14th century AD) and with a number of modern southern varieties of Chinese. In Middle Chinese, syllables closed with a stop consonant had no tone. However, Chinese linguists prefer to categorize such syllables as belonging to a separate tone class, traditionally called the "entering tone". Syllables closed with a glottal stop in Jin are still toneless, or alternatively, Jin can be said to still maintain the entering tone. In standard Mandarin Chinese, syllables formerly ending with a glottal stop have been reassigned to one of the other tone classes in a seemingly random fashion.

Jin employs extremely complex tone sandhi, or tone changes that occur when words are put together into phrases. The tone sandhi of Jin is notable in two ways among Chinese varieties:

Jin readily employs prefixes such as 圪 /kəʔ/, 黑 /xəʔ/, 忽 /xuəʔ/, and 入(日) /ʐəʔ/, in a variety of derivational constructions. For example:
入鬼 "fool around" < 鬼 "ghost, devil"

In addition, there are a number of words in Jin that evolved, evidently, by splitting a mono-syllabic word into two, adding an 'l' in between (cf. Ubbi Dubbi, but with /l/ instead of /b/). For example: