The first Mitsubishi company was a shipping firm that Yataro Iwasaki established in 1870. In 1873 it took the name Mitsubishi Shokai (三菱商会). The name Mitsubishi (三菱) has two parts: "mitsu" means "three" and "bishi" means "water chestnut", and hence "rhombus", which is reflected in the company's logo. Another translation is "three diamonds".
That company soon diversified into coal mining, shipbuilding, banking, insurance, warehousing, and trade. Later diversification carried the organization into such sectors as paper, steel, glass, electrical equipment, aircraft, oil, and real estate. As Mitsubishi built a broadly based conglomerate, it played a central role in the modernization of Japanese industry. 
At the start of the 20th century the company, which by itself accounted for over half of the Japanese merchant fleet, entered into a period of diversification that would eventually result in the creation of three entities:
- Mitsubishi Bank (now a part of the Mitsubishi UFJ Financial Group) was founded in 1919. After its mergers with the Bank of Tokyo in 1996, and UFJ Holdings in 2004, this became Japan's largest bank.
- Mitsubishi Corporation, founded in 1893, serves the internal financing needs of the group
- Mitsubishi Heavy Industries, which includes these industrial companies.
World War II
During the Second World War, Mitsubishi manufactured aircraft, including the famous Zero that was used in the attack on Pearl Harbor on December 7, 1941 and many other occasions. Also, like many other large Japanese corporations at that time, it made use of slave labor from U.S. Allied POWs and the Japanese captured territories, like Korea and China. With poor working conditions, many people died during this period. Approximately twenty thousand Korean slave laborers died in the atomic bombings of Hiroshima and Nagasaki by the United States.
In a statement, the Mitsubishi Corporation says that forced labor is inconsistent with the company's values, and that the various lawsuits targeting Mitsubishi are misdirected. Instead, a spokesman says the Mitsubishi of World War II is not the same Mitsubishi of today. The conglomerate also rejected a Chinese slave labor lawsuit demand by saying it bore no responsibility since it was national policy to employ Chinese laborers."
After the war
Mitsubishi split itself into independent companies in 1946 under the postwar government policy of decentralizing industry. The newly independent companies used their accumulated technology and other strengths to pursue growth under separate business models. As independent corporations, the Mitsubishi companies cooperated in some ventures, as in petrochemicals and nuclear power, and competed with each other in other sectors. The Mitsubishi companies form a loose entity known as the Mitsubishi keiretsu, or Mitsubishi group.
Mitsubishi has been criticized for some of its corporate practices, most notably with respect to work-place discrimination, and environmental pollution. A disgruntled former employee, Kamal Sinha, has started a website called Mitsubishi Watch to report such complaints. Niall Murtagh's book, "The Blue-Eyed Salaryman", describes both positive and negative aspects of working for Mitsubishi from a foreigner's perspective.
A new era
Mitsubishi participated in Japan's unprecedented economic growth of the 1950s and 1960s. For example, as Japan modernized its energy and materials industries, the Mitsubishi companies created Mitsubishi Petrochemical, Mitsubishi Atomic Power Industries, Mitsubishi Liquefied Petroleum Gas, and Mitsubishi Petroleum Development.
The traditional Mitsubishi emphasis on technological development was in new ventures in such fields as space development, aviation, ocean development, data communications, computers, and semiconductors. Mitsubishi companies also were active in consumer goods and services.
In 1970, Mitsubishi companies established the Mitsubishi Foundation to commemorate the centennial anniversary of the founding of the first Mitsubishi company. The companies also individually maintain charitable foundations. Mitsubishi pavilions have been highlights of expositions in Japan since the historic EXPO'70 in Osaka in 1970.
The Mitsubishi companies
- Asahi Glass Co.
- The Bank of Tokyo-Mitsubishi UFJ, Ltd.
- Kirin Brewery Co., Ltd.
- Meiji Yasuda Life Insurance Company
- Mitsubishi Agricultural Machinery
- Mitsubishi Aluminum Co., Ltd.
- Mitsubishi Cable Industries, Ltd.
- Mitsubishi Chemical Corporation (part of Mitsubishi Chemical Holdings Corporation)
- Mitsubishi Corporation (Trading company)
- Mitsubishi Electric Corporation
- Mitsubishi Estate Co., Ltd.
- Mitsubishi Fuso Truck and Bus Corporation
- Mitsubishi Gas Chemical Company, Inc.
- Mitsubishi Heavy Industries, Ltd.
- Mitsubishi Kakoki Kaisha, Ltd.
- Mitsubishi Logistics Corporation
- Mitsubishi Materials Corporation
- Mitsubishi Motors (Automobile manufacturing and sales)
- Mitsubishi Paper Mills, Ltd.
- Mitsubishi Plastics, Inc.
- Mitsubishi Rayon Co., Ltd.
- Mitsubishi Research Institute, Inc.
- Mitsubishi Shindoh Co., Ltd.
- Mitsubishi Steel Mfg. Co., Ltd.
- Mitsubishi UFJ Trust and Banking Corporation (part of Mitsubishi UFJ Financial Group)
- Nikon Corporation
- Nippon Oil Corporation
- NYK Line (Nippon Yusen Kabushiki Kaisha)
- P.S. Mitsubishi Construction Co., Ltd.
- Tokio Marine & Nichido Fire Insurance Co., Ltd.
- Atami Yowado
- Chitose Kosan Co., Ltd.
- The Dia Foundation for Research on Ageing Societies
- Diamond Family Club
- Koiwai Noboku Kaisha, Ltd.
- LEOC JAPAN Co., Ltd.
- Marunouchi Yorozu Corp.
- Meiwa Corporation
- Mitsubishi C&C Research Association
- Mitsubishi Club
- Mitsubishi Corporate Name and Trademark Committee
- Mitsubishi Economic Research Institute
- The Mitsubishi Foundation
- Mitsubishi Kinyokai
- Mitsubishi Marketing Association
- Mitsubishi Research and Development of America
- Mitsubishi Public Affairs Committee
- The Mitsubishi Yowakai Foundation
- MT Insurance Service Co., Ltd.
- Seikado Bunko Art Museum
- Shonan Country Club
- Sotsu Corporation
- The Toyo Bunko