The Sun has the largest circulation of any daily newspaper in the United Kingdom, but in late 2013 slipped to second largest Saturday newspaper behind the Daily Mail. In January 2018 it had an average daily circulation of 1.5 million. The Sun has been involved in many controversies in its history, including its coverage of the 1989 Hillsborough football stadium disaster. Regional editions of the newspaper for Scotland, Northern Ireland and the Republic of Ireland are published in Glasgow (The Scottish Sun), Belfast (The Sun) and Dublin (The Irish Sun) respectively.
On 26 February 2012, The Sun on Sunday was launched to replace the closed News of the World, employing some of its former journalists. The average circulation for The Sun on Sunday in March 2014 was 1,686,840; but in May 2015 The Mail on Sunday sold more copies for the first time, an average of 28,650 over those of its rival: 1,497,855 to 1,469,195. Roy Greenslade issued some caveats over the May 2015 figures, but believed the weekday Daily Mail would overtake The Sun in circulation during 2016.
The Sun was first published as a broadsheet on 15 September 1964, with a logo featuring a glowing orange disc. It was launched by owners IPC (International Publishing Corporation) to replace the failing Daily Herald.
Research commissioned by Cecil King from Mark Abrams of Sussex University, The Newspaper Reading Public of Tomorrow, identified demographic changes which suggested reasons why the Herald might be in decline. The new paper was intended to add a readership of "social radicals" to the Herald's "political radicals". Supposedly there was "an immense, sophisticated and superior middle class, hitherto undetected and yearning for its own newspaper", wrote Bernard Shrimsley of Abrams' work forty-years later. "As delusions go, this was in the El Dorado class". Launched with an advertising budget of £400,000, the brash new paper "burst forth with tremendous energy", according to The Times. Its initial print run of 3.5 million was attributed to "curiosity" and the "advantage of novelty", and had declined to the previous circulation of the Daily Herald (1.2 million) within a few weeks.
By 1969, according to Hugh Cudlipp, The Sun was losing about £2m a year and had a circulation of 800,000. IPC decided to sell to stop the losses, according to Bernard Shrimsley in 2004, out of a fear that the unions would disrupt publication of the Mirror if they did not continue to publish the original Sun. Bill Grundy wrote in The Spectator in July 1969 that although it published "fine writers" in Geoffrey Goodman, Nancy Banks-Smith and John Akass among others, it had never overcome the negative impact of its launch at which it still resembled the Herald. The pre-Murdoch Sun was "a worthy, boring, leftish, popular broadsheet" in the opinion of Patrick Brogan in 1982.