Oracle bone script is the oldest attested form of written Chinese, dating to the late 2nd millennium BC. Inscriptions were made by carving characters into oracle bones, usually either the shoulder bones of oxen or the plastrons of turtles. The writings themselves mainly record the results of official divinations carried out on behalf of the Late Shang royal family. These divinations took the form of scapulimancy where the oracle bones were exposed to flames, creating patterns of cracks that were then subjected to interpretation. Both the prompt and interpretation were inscribed on the same piece of bone that had been used for the divination itself.

Out of an estimated 150,000 inscriptions that have been uncovered, the vast majority were unearthed at Yinxu, the site of the final Shang capital (modern-day Anyang, Henan). The most recent major discovery was the Huayuanzhuang cache found near the site in 1993. Of the 1,608 Huayuanzhang pieces, 579 bear inscriptions. Each of the last nine Shang kings are named in the inscriptions beginning with Wu Ding, whose accession is variously dated between 1250 and 1200 BC. Oracle bone inscriptions corresponding to Wu Ding's reign have been radiocarbon dated to 1254–1197 BC (±10 years). Following the overthrow of the Shang by the Zhou dynasty in c. 1046 BC, divination using milfoil became more common; far fewer oracle bone inscriptions are dated to the Western Zhou. No Zhou-era sites with a comparable cache of inscriptions to Yinxu have been found; however, examples from this period appear to be more widespread, having been found near most major population centers. New sites have continued to be discovered since 2000.

The oracle bone inscriptions—along with several roughly contemporaneous bronzeware inscriptions using a different style—constitute the earliest corpus of Chinese writing, and are the direct ancestor of the Chinese family of scripts developed over the next three millennia. Their study is essential for the research of Chinese etymologies. It is also the direct ancestor of over a dozen East Asian writing systems. The length of inscriptions ranges from 10 to over 100 characters, but a few dozen is typical. The subjects of concern in inscriptions are broad, and include war, ritual sacrifice, and agriculture, as well as births, illnesses, and deaths in the royal family. As such, they provide invaluable insights into the character of late Shang society.

The common Chinese term for oracle bone script is 甲骨文 (jiǎgǔwén 'shell and bone script'), which is an abbreviation of 龜甲獸骨文字 (guījiǎ shòugǔ wénzì 'turtle-shell and animal-bone script'). This term is a translation of the English phrase "inscriptions upon bone and tortoise shell", which had been coined by the American missionary Frank H. Chalfant (1862–1914) in his 1906 book Early Chinese Writing, which first appeared in Chinese books during the 1930s. In earlier decades, Chinese authors used a variety of names for the inscriptions based on the name of Yinxu, their purpose (卜 bǔ 'to divine'), or the method of inscription (契 qì 'to engrave'). A previously common term was 殷墟卜辭 (Yīnxū bǔcí 'Yinxu divinatory texts').

Oraculology (甲骨学; 甲骨學; jiǎgǔxué) is the study of oracle bones and oracle bone script. It is a humanities discipline that focuses on the Chinese Upper Antiquity oracle characters. Oracle bone science can be divided into a narrow sense of oracle bone science and a broad sense of oracle bone science. In the narrow sense, the study of oracle bone script is limited to the study of oracle bone script itself, and it is a discipline of paleography. This includes the integration of theories, research methods and materials from various disciplines, such as paleography, history, archaeology, historical culture, historical literature, and cultural anthropology, to thoroughly study the historical and cultural background of the oracle bones and some of the patterns of the oracle bone divination. It is a diversified and specialized discipline. In the early days of oracle bone discovery, oracle bones were called qiwen, and the study of oracle bones was called qiology. In 1931, Zhou Yitong proposed for the first time that "oracle bone science" was an independent discipline. Wang Yuxin emphasized that oracle bones are precious cultural relics and historical materials left over from the ancient period, but their value for archaeological and historical research lies in orthography beyond script interpretation, which has become increasingly recognized by scholars as orthography develops. Oracle bone science is a systematic and scientific inquiry into the inherent laws of the oracle bone script itself and uses it as a basis for glimpsing the history, society, and customs of the ancient world. The oracle bones should not be confused with orthography.

It is generally agreed that the tradition of writing represented by oracle bone script existed prior to the first known examples, due to the attested script's mature state. Many characters had already undergone extensive simplifications and linearizations, and techniques of semantic extension and phonetic loaning had also clearly been used by authors for some time, perhaps centuries. However, no clearly identifiable examples of writing dating prior to the 13th century BC have been discovered. Sets of inscribed symbols on pottery, jade, and bone that have been discovered at a variety of Neolithic archeological sites across China have not been demonstrated to have any direct or indirect ancestry to the Shang oracle bone script at Anyang.

Along with the contemporary bronzeware script, the oracle bone script of the Late Shang period appears pictographic. The earliest oracle bone script appears even more so than examples from late in the period (thus some evolution did occur over the roughly 200-year period). Comparing the oracle bone script to both Shang and early Western Zhou period writing on bronzes, the oracle bone script is clearly greatly simplified, and rounded forms are often converted to rectilinear ones; this is thought to be due to the difficulty of engraving the bone's hard surface, compared with the ease of writing them in the wet clay of the molds the bronzes were cast from. The more detailed and more pictorial style of the bronze graphs is thought to be more representative of typical Shang writing using bamboo books than the oracle bone forms; this typical style continued to evolve into writing styles of the Western Zhou period, and then into the seal script within the state of Qin.

It is known that the Shang people also wrote with brush and ink, as brush-written graphs have been found on a small number of pottery, shell and bone, and jade and other stone items, and there is evidence that they also wrote on bamboo (or wooden) books just like those found from the late Zhou to Han periods, because the graphs for a writing brush (聿 yù, depicting a hand holding a writing brush) and bamboo book (冊 cè, a book of thin bamboo and wooden slips bound with horizontal strings, like a Venetian blind turned 90 degrees), are present in oracle bone inscriptions.