The Mitsui family (三井家) is a Japanese banking and business family who established the Mitsui Group.
The Mitsui enterprise (present-day Mitsui Group) was established in 1673 when Mitsui Takatoshi (1622–1694), the son of merchant parents, established Echigoya, a dry goods department store in both Edo and Kyoto, which later became the Mitsukoshi department store chain. Meeting with great success, Takatoshi extended his services to moneylending and exchange.
In the late Edo period, the Mitsuis were the richest and most eminent family in Japan, their business being thoroughly encouraged by the shogunal government of the time. After the Meiji Restoration, the family switched allegiance to the Meiji government.
In 1909, a Mitsui controlled holding company took over the business, with Mitsui thus becoming a zaibatsu (business conglomerate) of more than 150 companies, and in modern times the group counts dozens of multinational companies in fields such as trade, banking, shipping and shipbuilding, construction, mining, oil and gas, insurance, chemicals and real estate development.