Westpac (formally Westpac Banking Corporation), is a multinational Financial services company an the third largest bank in Australia (by market capitalization). Westpac has also been recognized by the Dow Jones Sustainability Index as the most sustainable bank in the world for the fifth year running. The bank is one of the Australian 'big four' banks, joining NAB, ANZ, and the Commonwealth Bank as the main providers of financial services to Australians.