The Mitsui Group and the Mitsui Bunko Public Interest Incorporated Foundation have been working since 2023 on the “Digital Archive Project for Historical Materials Held by Mitsui Bunko,” commemorating the 350th anniversary of the Mitsui Group. The project is creating digital images of about 30,000 items from Mitsui Bunko’s holdings, including early modern materials such as Mitsui family records and modern corporate materials from Mitsui Bank, the former Mitsui & Co. (Note 1), and Mitsui Mining. Preparations have now been completed to release about 15,000 images related to Mitsui’s business history, and online publication will begin on Monday, May 18. The materials to be released cover Mitsui’s business activities in the early modern period, namely the Edo period, and the modern period from the Meiji era through the dissolution of the zaibatsu. They are valuable resources for understanding Japanese business history, economic history, and modern and contemporary history. The archive includes large-scale releases of images such as the Omotokata Kanjo Mokuroku, Mitsui’s early modern consolidated settlement ledgers that show business trends over roughly 160 years from 1710, and the Osaka Ryogaedana Nikkiroku, business diaries of the Osaka money exchange shop that record daily operations as well as weather, daily rice prices, and exchange rates. This is Mitsui Bunko’s first initiative to publish digital images of its holdings online, and it represents an unprecedented scale of release. Through this online publication, Mitsui’s historical materials can now be shared worldwide. The archive is expected to be used by a wide range of people, including researchers in Japan and abroad studying Japanese business history, economic history, and modern and contemporary history; teachers from elementary through high school; students interested in Japanese and economic history; general users researching family history; and those involved in compiling corporate histories and local gove