The Commonwealth Bank of Australia was founded by the Commonwealth Bank Act on 22 December 1911, introduced by the Andrew Fisher Labor Government, which favored bank nationalization. In a rare move for the time, the bank was to have both savings and general bank business. The bank was also the first bank in Australia to receive a Federal Government guarantee. The bank's earliest and most strenuous proponent was the flamboyant American-Australian Labor politician, King O'Malley, and its first Governor was Sir Denison Miller. The bank opened its first branch in Melbourne on 15 July 1912. In an agreement with Australia Post that exists to this day, the bank also traded through post office agencies. In 1912, it merged with the state savings bank in Tasmania, and by 1913 it had branches in all six states.

Presently, The Commonwealth Bank of Australia is an Australian multinational bank with businesses across New Zealand, Fiji, Asia, the United States and the United Kingdom. Commonly referred to as the Commonwealth Bank (or CBA or Commbank), it provides a variety of financial services including retail, business and institutional banking, funds management, superannuation, insurance, investment and broking services. The Commonwealth Bank is the largest Australian listed company on the Australian Securities Exchange as of August 2015 with brands including Bankwest, Colonial First State Investments Limited, ASB Bank (New Zealand), Commonwealth Securities Limited (CommSec) and Commonwealth Insurance Limited (CommInsure). Commonwealth Bank is also the largest bank in the Southern Hemisphere. Founded in 1911 by the Australian government, the Commonwealth Bank is one of the "big four" Australian banks, with National Australia Bank (NAB), ANZ and Westpac. The bank listed on the Australian Stock Exchange in 1991 and the government fully privatized it in 1996. The former global headquarters of Commonwealth Bank were the Commonwealth Trading Bank Building on the corner of Pitt Street and Martin Place, which was refurbished from 2012 for retail and commercial uses, and (from 1984 to 2012) the State Savings Bank Building on Martin Place, which was sold in 2012 to Macquarie Bank. The headquarters were moved to Tower 1, 201 Sussex Street. Additionally, two new nine-storey buildings which were built at the site of the former Sega World Sydney, in Darling Harbour on the western side of Sydney's city centre.