National Australia Bank

National Australia Bank Limited (abbreviated NAB, branded and stylised as nab) is one of the four largest financial institutions in Australia (colloquially referred to as "The Big Four") in terms of market capitalisation, earnings and customers. NAB was ranked the world's 21st-largest bank measured by market capitalisation and 52nd-largest bank in the world as measured by total assets in 2019.

As of January 2019^[update], NAB operated 3,500 Bank@Post locations—including 7,000+ ATMs across Australia, New Zealand, and Asia—and served 9 million customers.

NAB has an "AA−" long-term issuer rating by Standard & Poor's.

National Australia Bank was formed as National Commercial Banking Corporation of Australia Limited in 1982 by the merger of National Bank of Australasia and the Commercial Banking Company of Sydney. The resulting company was subsequently renamed National Australia Bank Limited.

The expanded financial base of the merged entity triggered significant offshore expansion over ensuing years. Representative offices were established in Beijing (1982), Chicago (1982), Dallas (1983), Seoul (1983, upgraded to a branch in 1990), San Francisco (1984), Kuala Lumpur (1984), Athens (1984, closed 1989), Frankfurt (1985, closed 1992), Atlanta (1986), Bangkok (1986), Taipei (1986 upgraded to branch 1990), Shanghai (1988, closed 1990), Houston (1989) and New Delhi (1989).

In 1987, NAB bought Clydesdale Bank (Scotland) and Northern Bank (Northern Ireland and Republic of Ireland) from Midland Bank. It rebranded Northern Bank branches in the Republic of Ireland to National Irish Bank and changed both banks' logos from that of the Midland Bank. In 1990, NAB bought Yorkshire Bank (England and Wales).

In 1992, NAB purchased the Bank of New Zealand, which became a subsidiary of the Australian bank, but retained local governance, with a New Zealand board of directors. At some point, a business entity known as Bank of New Zealand in Australia (BNZA) was absorbed by NAB.

Further acquisitions followed – which at the time had about a 26% market share in the market, and Michigan National Bank (MNB) in 1995. NAB had earlier rationalised its operations in the US and closed its offices in Atlanta, Chicago, Dallas, Houston and San Francisco in 1991.