Which car company was founded by Soichiro Honda?

The car company founded by Soichiro Honda was Honda, formally Honda Motor Co., Ltd.

Soichiro Honda established Honda Motor Co., Ltd. in Japan in 1948 with business partner Takeo Fujisawa. The company began by producing motorized bicycles and motorcycles, building a reputation for practical engineering and strong performance before entering automobile manufacturing.

Honda’s roots go back further: in 1937, Soichiro Honda founded Tōkai Seiki to make piston rings, including parts supplied to Toyota. After the Second World War, he used the proceeds from selling that business’s remains to help establish the Honda Technical Research Institute, which led to Honda’s postwar expansion.

The answer is Honda rather than Toyota, even though Toyota once held a stake in Tōkai Seiki and Honda supplied it with piston rings. Honda became an automobile producer later, but motorcycles were central to its early growth and global identity.