Mizuho Holdings (TSE 8305) is the largest banking company in the world. It is headquartered in the Marunouchi district of Tokyo, and has assets totalling nearly $1.3 trillion. Mizuho was formed from the merger of Dai-Ichi Kangyo, Fuji Bank, and the Industrial Bank of Japan, three of Japan's largest banks in their own right, in an attempt to consolidate their scores of bad loans. The three banks sold themselves to Mizuho in September of 2000, and finished their consolidation in 2002.

In reality, Mizuho consists of two banks: Mizuho Bank, with 30 million personal accounts, and Mizuho Corporate Bank, with seventy percent of the Tokyo Stock Exchange as its clientele. Each is roughly the size of the Bank of America or HSBC.

Following the Mizuho merger, there are only four large banks left in Japan: Mizuho, SMBC, MTFG, and UFJ. Many analysts believe that the Japanese finance industry has come as close to oligopoly as it can realistically withstand, but in Japan's post-bubble slump, nobody is telling the banks to stay divided.

In Japanese, mizuho means "fresh harvest of rice," and is sometimes used in poetry to evoke images of Japan as a wealthy nation.