The Mitsubishi company was established as a shipping firm by Iwasaki Yatarō  in 1870 under the name "Tsukumo Shokai.  In 1873, its name was changed to Mitsubishi Shokai: "mitsu", meaning "three" (as in the three oak leaves from the crest of the Yamauchi or Tosa family that ruled over Yatarō's birthplace and employed him) and "hishi", which becomes "bishi" under rendaku) meaning "water caltrop", and hence "rhombus", which is reflected in the company's logo. It is also translated as "three diamonds".

In 1934, Mitsubishi Shipbuilding was merged with the Mitsubishi Aircraft Co., a company established in 1920 to manufacture aircraft engines and other parts. The unified company was known as Mitsubishi Heavy Industries (MHI), and was the largest private company in Japan. MHI concentrated on manufacturing aircraft, ships, railroad cars and machinery, but in 1937 developed the PX33, a prototype sedan for military use. It was the first Japanese-built passenger car with full-time four-wheel drive, a technology the company would return to almost 50 years later in its quest for motorsport and sales success.

Earlie 60s Mitsubishi introduced the Mitsubishi 500, a mass-market sedan, to meet the new demand from consumers. It followed this in 1962 with the Minica kei car and the Colt 1000, the first of its Colt line of family cars, in 1963. In 1964, Mitsubishi introduced its largest passenger sedan, the Mitsubishi Debonair as a luxury car primarily for the Japanese market, and was used by senior Mitsubishi executives as a company car.

Mitsubishi Pajero (youtube.com)