The Guardian was first published in May 1821 - it was then known as the Manchester Guardian.

In June 1936, JR Scott formally passed ownership of the paper to the trustees of the Scott Trust. As well as pledging to ensure the radical editorial tradition of the paper (that the newspaper "shall be conducted in the future on the same lines and in the same spirit as heretofore", in the words of the founder's legacy), the Scott Trust also has the duty to maintain a secure financial footing for the business: "...to devote the whole of the surplus profits of the Company which would otherwise have been available for dividends...towards building up the reserves of the Company and increasing the circulation of and expanding and improving the newspapers." These principles remain the only instructions given to an incoming editor of the Guardian.

In the increasingly polarised political climate of the late 1970s and early 1980s the Guardian's position as the voice of the left was unchallenged. The opinion pages were the birthplace of the SDP, and the letters page was where the battle for the future direction of the Labour Party was played out, while the coverage of industrial disputes including the 1984-1985 Miners' Strike defined the paper's position.

In 1993-94 the Guardian’s main competitors in the UK market reduced their cover price as they battled to survive. Throughout this period the Guardian remained at full price, investing resources in journalism and distancing itself from the price war through distinctive and innovative marketing, product development and consistently breaking big stories.

In 1994-95 the Guardian began developing online publication, and in January 1999 the Guardian Unlimited network of websites was launched as a unified whole (in 2008 it was to become guardian.co.uk and in 2013 theguardian.com). By March 2001 GU had over 2.4 million unique users, making it the most popular UK newspaper website.

In December 2008 the Guardian moved to a brand new building in King's Cross after 32 years in its Farringdon headquarters. In 2011 the Guardian was recognised at the Press Awards where it was named Newspaper of the Year for its partnership with WikiLeaks, which produced the leaked US embassy cables. In the same year the Guardian made headlines with its globally acclaimed investigation into phone hacking.