Nationwide Building Society is a British mutual financial institution, the seventh largest cooperative financial institution and the largest building society in the world with over 16 million members. Its headquarters are in Swindon, England. Nationwide is made up of around 250 different building societies. Among the most significant mergers were those with the Anglia Building Society in 1987 and the Portman Building Society in 2007. It is now the second largest provider of household savings and mortgages in the UK and has a 10.3% market share of current accounts for the 2021/2022 financial year. For the financial year 2021/2022, Nationwide had assets of around £272.4 billion compared to £483 billion for the entire building society sector, making it larger than the remaining 42 British building societies combined. It is a member of the Building Societies Association, the Council of Mortgage Lenders and Co-operatives UK. Wikipedia