Cai Lun (Chinese: 蔡伦; courtesy name: Jingzhong; c. 50–62 – 121 CE), also known as Ts'ai Lun, was a Chinese eunuch court official during the Eastern Han dynasty. He played an important role in the history of paper because he added tree bark and hemp waste to the papermaking process. This innovation allowed for the large-scale production of paper, which spread widely across the world. While he is often called the inventor of paper, earlier forms of paper existed as early as the 3rd century BCE. Therefore, Cai’s contribution was to improve the process, not to invent paper itself.
Cai was born in Guiyang Commandery (now Leiyang). By 75 CE, he had arrived at the imperial court in Luoyang, where he worked as a chamberlain for Emperor Ming and later as an imperial messenger for Emperor Zhang. To help Lady Dou secure her adopted son as the heir, Cai questioned Consort Song and her sister, who later committed suicide. When Emperor He took the throne in 88 CE, Lady Dou gave Cai two important positions: Zhongchang shi, a top political advisor for eunuchs, and Shangfang Ling, where he managed the production of tools and weapons at the Palace Workshop.
Although Emperor He successfully removed the Dou family from power in 92 CE, Cai remained unaffected by the downfall of his former ally. His role at the Palace Workshop expanded, and he oversaw the creation of ceremonial weapons, which were noted for their high quality. His most famous innovation came in 105 CE, when he improved the papermaking process by using tree bark, hemp waste, old cloth, and fishnets. This new type of paper replaced earlier materials like bamboo and wooden slips, and Cai gained wealth and recognition across the empire.
In 110 CE, Lady Deng, who became the empress dowager for the young Emperor An, appointed Cai to lead 100 scholars in producing a new version of the Five Classics. In 114 CE, Cai was rewarded for his service with the title of marquis and was given control of Longting, a small village. However, in 121 CE, after Lady Deng died, Cai was ordered to the Ministry of Justice due to his involvement in the death of the emperor’s grandmother, Consort Song. Feeling ashamed and fearing punishment, Cai committed suicide that year and died in Luoyang, the city where he had lived most of his adult life.
Cai’s improvements to papermaking had a major impact on human history. He is the only early figure among China’s Four Great Inventions—compass, gunpowder, papermaking, and printing—whose name is known. In China, he is honored in ancestor worship, worshipped as the god of papermaking, and appears in folklore. His hometown in Leiyang continues to be a center for paper production.
Life and career
Cai Lun was born in Guiyang Commandery (modern-day Leiyang, Hunan province) during the Eastern Han dynasty (25–220 CE). His exact birth year is unknown, but some estimates suggest he was born around 50, 57, or 62 CE. Little is known about his early life, except that he was born into a poor family. Guiyang was a southern region where Han Chinese had lived for many years, growing rice. Stories say there was a pool near his home, and south of it was a stone mortar that Cai would later use in papermaking.
It is unclear how Cai traveled to Luoyang (modern-day Luoyang, Henan province), the imperial capital, which was far from his birthplace. The Hou Hanshu records that he was first employed during the end of the Yongping era (58–75 CE) under Emperor Ming. At the time, Guiyang Commandery had iron mines, so the former director of the Paper Museum in Tokyo, Kiyofusa Narita, suggested that Cai may have been helped by people working in the iron foundry to reach the capital. Narita noted that Cai’s later court role in overseeing weapon production, especially swords, suggests he likely learned these skills earlier in life, possibly through the iron foundry. Alternatively, some folktales claim Cai used trickery to gain a court position.
Cai became a eunuch in 75 CE, though he may have been employed earlier in the Yongping era. In the Han dynasty, eunuchs worked in the imperial court and were eligible for specialized tasks, such as overseeing the imperial harem or managing the household. Cai’s role likely involved acting as a liaison between the privy council and the emperor, similar to a chamberlain. Around 80 CE, during the Jianchu era (76–84 CE) under Emperor Zhang, Cai was promoted to Xiao Huangmen ("Attendant at the Yellow Gates"), a position with a salary rank of 600 shi. This role involved delivering and receiving messages between the palace and the outside court.
In 79 CE, Liu Qing, Emperor Zhang’s son from his concubine Consort Song, was the designated heir, supported by Empress Ma. However, after Ma’s death later that year, Lady Dou became empress and aimed to strengthen her family’s power by adopting Prince Zhao and trying to make him the heir. When Consort Song fell ill in 82 CE and asked for herbs, Lady Dou falsely accused her of using the herbs for witchcraft against Emperor Zhang. Dou ordered Cai to interrogate Consort Song and her sister, another imperial consort, forcing them to confess. Both women committed suicide, and Emperor Zhang replaced Liu Qing with Prince Zhao as heir.
Prince Zhao, who became Emperor He at age 10 in 88 CE, was controlled by Lady Dou, who gave positions to her brothers, especially Dou Xian. Dou Xian promoted Cai to Zhongchang shi ("Regular Attendant"), a high-ranking eunuch position with a salary rank of 2000 shi. Cai served as a political advisor to Emperor He and later became Shangfang Ling ("Prefect of the Palace Workshop"), overseeing the production of imperial instruments and weapons. This role had a salary rank of 600 shi, in addition to his Zhongchang shi position.
In 92 CE, Emperor He came of age and led a coup to remove the Dou family from power. Cai was not involved in this action, and though he had previously supported the family, he was not affected by the coup. In 97 CE, his role as Shangfang Ling expanded to include responsibility for ceremonial swords and other items. The Hou Hanshu praised his craftsmanship as high-quality and a model for future generations.
Writing in China had a long history, with bamboo and wooden slips being common writing surfaces. These were inconvenient to use and store. Silk and cloth later became alternatives but were too expensive. In 105 CE, Cai publicly announced he had invented a new papermaking process. His method used bamboo, hemp waste, old rags, fishnets, and tree bark (likely mulberry). The materials were boiled into pulp, beaten with a wooden or stone tool, mixed with water, and processed with wooden sieves to remove excess water. The resulting paper, called "Cai Hou paper," became widely used. This event is described in the Hou Hanshu.
Legends suggest Cai was inspired by watching paper wasps build nests or by people in his hometown using mulberry bark to make cloth for writing. Regardless of the inspiration, his process impressed Emperor He and gained him fame.
After Emperor Shang’s short reign in 106 CE, Emperor He was succeeded by 13-year-old Emperor An, who was ruled by Lady Deng. Cai and Zheng Zhong remained influential in Deng’s court. In 110 CE, Deng gathered over 100 scholars to create a definitive version of the Five Classics, and Cai oversaw the project. In 114 CE, Cai was awarded the title of marquis and became the lord of Longting, a small village in modern-day Shaanxi. After Zheng Zhong died, Cai became head of the Dowager’s household.
When Lady Deng died in 121 CE, Emperor An took power, but the court was controlled by Empress Yan Ji and her family. Remembering Cai’s role in the death of his grandmother, Consort Song, Emperor An ordered Cai to face charges and likely face execution. Ashamed, Cai dressed formally and drank poison to take his own life.
Legacy
Modern archaeological studies have shown that different types of paper existed in China as early as the 3rd century BCE. However, these findings do not change the recognition of Cai Lun for his contributions. A Chinese scholar named Tsien Tsuen-hsuin explained that the term "zào yì" (造意) in Cai's ancient biography means "to initiate the idea," which suggests he improved an existing process by adding important materials. Cai Lun is known for using tree bark and hemp to make paper, and his improvements made paper widely used in China. Scholars now believe Cai Lun advanced an ongoing process rather than creating paper from nothing. Despite this, he is still traditionally credited with inventing paper because his changes were very important and helped spread paper use throughout China. Some people think Cai Lun may have taken credit for someone else's work, similar to how Feng Dao is believed to have done with printing improvements.
Cai Lun’s papermaking methods had a major impact on human history. They helped spread knowledge and improved communication worldwide. However, Cai Lun is not well known outside East Asia and is often left out of major encyclopedias. A scholar named Thomas Francis Carter compared Cai Lun to Johannes Gutenberg, the inventor of the first printing press with movable type, calling them "spiritual father and son." In 1978, Michael H. Hart ranked Cai Lun 7th in his book The 100: A Ranking of the Most Influential Persons in History, placing him above figures like Gutenberg, Christopher Columbus, Albert Einstein, and Charles Darwin. In 2007, Time magazine included Cai Lun in its list of the "Best Inventors" of all time.
After Cai Lun’s work in 105 CE, a papermaker who may have been his apprentice—named Zuo Bo, Tso Po, or Tso Tzǔ-yi—improved the process in the 150s CE during the Han dynasty. The basic principles of Cai Lun’s papermaking method changed little over time, and paper spread throughout China. According to legend, a Buddhist monk named Damjing brought the process to Japan, though this is not confirmed. Damjing is considered a patron saint in Japan, similar to how Cai Lun is seen in China. By the 600s, papermaking reached Turkestan, Korea, and India. Chinese prisoners from the Battle of Talas shared the knowledge with Arabs in the Abbasid Caliphate. Unlike many Chinese inventions that were developed independently in Europe, papermaking was a Chinese creation that spread to Europe through the Arabs. By the 12th century, paper was widely made in Europe. In 2010, the International Astronomical Union honored Cai Lun by naming a moon crater after him.
Little is known about Cai Lun’s personal life, but a popular story suggests he was a shopkeeper with a wife and brother. After his paper improvements, he had too much paper to sell, so he and his wife tricked townspeople into buying it by claiming that burning paper would turn it into money in the afterlife. In one version of the story, Cai’s brother and sister-in-law, Cai Mo and Hui Niang, take his place. Hui Niang pretended to die, and Cai Mo burned paper as tribute. When neighbors saw this, they believed the story and bought paper for their own use. While the story is fictional, burning offerings and loud mourning are common in Chinese culture.
Cai Lun is the only early figure known among China’s Four Great Inventions: papermaking, printing, the compass, and gunpowder. Compared to other inventions like the writing brush and ink, papermaking has the best historical records.
After Cai Lun died in 121 CE, a shrine and grave were built in his hometown, but they were later damaged by floods and forgotten. During the Tang dynasty, Cai Lun was deified as the national god of papermaking, and his image appeared on paper mills and shops in China and Japan. In 1267, a man named Chen Tsunghsi restored Cai Lun’s shrine, adding a statue and mausoleum. A stone mortar, said to be used by Cai Lun, may have been placed in the mausoleum or in the Imperial Museum. The shrine was later restored in 1955 and still stands today as the Cai Lun Temple near Leiyang, renamed "Cai Lun Pool." In the Song dynasty, a temple in Chengdu became a place where papermakers worshipped Cai Lun.
During the late Qing dynasty, papermakers formed religious groups called "spirit-money associations" or "Cai Lun associations." In 1839, a conflict arose in Sichuan when one group claimed ritual superiority over others. A county official reminded them that they all owed their livelihood to Cai Lun and should share the benefits of the trade.
Today, Leiyang is still known as Cai Lun’s birthplace and has active paper production. His traditional tomb is located in the Cai Lun Paper Culture Museum in Hanzhong, Shaanxi. In modern China, Cai Lun’s name is linked to paper, and there are at least five roads named after him in cities like Shanghai, Hangzhou, Xi’an, and Hefei.