Nationwide Building Society is a British mutual financial institution and the largest building society in the world. It has its headquarters in Swindon, with an office in Threadneedle Street, London, and with administration centres based in Bournemouth, Northampton and Dunfermline. For the financial year 2015/2016, Nationwide had assets of around £208.9 billion compared to £331 billion for the entire building society sector, making it larger than the remaining 44 British building societies combined.