The Zuo Zhuan (Chinese: 左傳; Wade–Giles: Tso Chuan; [tswò ʈʂwân]), often translated as The Zuo Tradition or as The Commentary of Zuo, is an ancient Chinese narrative history traditionally regarded as a commentary on the ancient Chinese chronicle Spring and Autumn Annals. It comprises 30 chapters that cover the period from 722 to 468 BC, and it focuses mainly on the Chinese political, diplomatic, and military affairs from that era.

For many centuries, the Zuo Zhuan was the primary text through which educated Chinese learned their ancient history. The Zuo Zhuan does not simply explain the wording of the Spring and Autumn Annals, but rather expounds upon its historical background with rich and lively accounts of the history and culture of the Spring and Autumn period (771–476 BC). The Zuo Zhuan is the source of more Chinese sayings and idioms than any other classical work, and its concise, flowing style served as a paragon of elegant Classical Chinese. Its tendency toward third-person narration and portraying characters through direct speech and action became hallmarks of Chinese narrative in general, and its style was imitated by historians, storytellers, and ancient-style prose masters for over 2000 years of subsequent Chinese history.

The Zuo Zhuan has a reputation as "a masterpiece of grand historical narrative", but its early textual history is largely unknown, and the nature of its original composition and authorship have been widely debated. The titular "Zuo" was traditionally identified as Zuo Qiuming—an obscure figure of the 5th century BC described as a blind disciple of Confucius—but there is little actual evidence to support this. Most scholars now generally believe that the Zuo Zhuan was originally an independent work, composed during the 4th century BC, that was later rearranged as a commentary to the Annals.

Despite its longstanding status as the paragon of Classical Chinese prose, little is known of the creation and early history of the Zuo Zhuan. Bamboo and silk manuscripts excavated from late Warring States period (c. 300 BC) tombs, combined with analyses of the language, diction, chronological references, and philosophical viewpoints of the Zuo Zhuan, suggest that its composition was largely complete by 300 BC. No pre-Han dynasty (202 BC – AD 220) sources, however, suggest that the Zuo Zhuan had to that point been organized into any coherent form. Pre-Han dynasty texts do not directly refer to the Zuo Zhuan as a source, although a few mention its parent text Spring and Autumn Annals. The Zuo Zhuan seems to have had no distinct title of its own during this period, but seems to have simply been called "Annals (Chunqiu)" along with a larger group of similar texts.

In the 3rd century AD, the Chinese scholar Du Yu intercalated the Zuo Zhuan with the Annals so that each Annals entry was followed by the corresponding narrative from the Zuo Zhuan. This became the received format of the Zuo Zhuan that exists today. Some modern scholars believe that the Zuo Zhuan originally was an independent work composed during the latter half of the 4th century BC—though probably incorporating some older material—that was later rearranged as a commentary to the Annals.

Sima Qian's 1st century BC Records of the Grand Historian, the first of China's 24 dynastic histories, refers to the Zuo Zhuan as "Master Zuo's Spring and Autumn Annals" (左氏春秋; Zuǒshì chūnqiū) and attributes it to a man named "Zuo Qiuming" (or possibly "Zuoqiu Ming"). According to Sima Qian, Confucius's disciples began disagreeing over their interpretations of the Annals after Confucius's death. Zuo therefore gathered together Confucius's scribal records and used them to compile the Zuo Annals in order to "preserve the true teachings." The "Zuo Qiuming" whom Sima Qian references was traditionally assumed to be the Zuo Qiuming who briefly appears in the Analects of Confucius when Confucius praises him for his moral judgment.

Other than this brief mention, nothing is concretely known of the life or identity of the Zuo Qiuming of the Analects, nor of what connection he might have with the Zuo Zhuan. This traditional assumption that the title's "Master Zuo" refers to the Zuo Qiuming of the Analects is not based on any specific evidence, and was challenged by scholars as early as the 8th century. Some modern scholars have observed that even if the Zuo Qiuming of the Analects is the "Zuo" referenced in the Zuo Zhuan′s title, this attribution is questionable because the Zuo Zhuan describes events from the late Spring and Autumn period (c. 771 – 476 BC) that Zuo could not have known.

Alternatively, a number of scholars, beginning in the 18th century, have suggested that the Zuo Zhuan was actually the product of Wu Qi, a military leader who served in the State of Wei and who, according to the Han Feizi, was from a place called Zuoshi (左氏). In 1792, the scholar Yao Nai wrote: "The [Zuo Zhuan] did not come from one person. There were repeated accretions and additions, with those of Wu Qi and his followers being especially numerous...."