1992 commercial for Nationwide Building Society.

Nationwide Building Society is a British building society, that is, as of 2009, the largest in the world. It has its headquarters in Swindon, England, and maintains a significant administration centre in Northampton. It is the only UK building society to clear its own cheques. Until mid-2009, when it announced the withdrawal of the service, it had been the only UK financial institution to offer completely fee-free transactions (both electronic and cash withdrawals) worldwide with its VISA debit cards. Nationwide was by far the largest British building society that did not convert to a bank in the wave of demutalisations that occurred from the late 1980s to the late 1990s. As of 2008, it is larger than all the other remaining British building societies combined, measured by total assets. It is a member of the Building Societies Association.

Nationwide Building Society provides financial services both directly, and through approximately 750 branches and 200 agencies. Nationwide is a major provider of both mortgages and savings in the UK, as well as personal banking and commercial lending. Nationwide.co.uk is the main website and sells most products and has around 2.5 million monthly visitors and 1.6 million active internet bankers. It also has a Sponsorship website at nationwidefootball.co.uk which replaced the previous Sponsored by You website on 7 January 2009.

The Society’s origins lie in Wiltshire (1846), Northampton (1848) and within the co-operative movement in London (1883). Over a hundred mergers later — most notably the merger between the Nationwide and the Anglia Building Society in 1987 — they are now the UK’s second largest mortgage lender and savings provider. More significantly, it is the largest building society in the world and committed to staying mutual. The society is keen to emphasise that it does not have shareholders, it has members.

In August 2007 the Society merged with Portman Building Society, creating a mutual body with assets of more than £160bn.

In the financial crisis of 2007–2009, the Nationwide has acted to safeguard the mutual sector, acquiring the ailing Cheshire and Derbyshire building societies in September 2008 and the Dunfermline Building Society on 30 March 2009. No member votes were taken, and no windfall benefit were given to society members. The Derbyshire, Cheshire and Dunfermline brand names will continue as separate trading arms of the Nationwide group.