The Sun is a daily tabloid newspaper published in the United Kingdom and Ireland (where it is known as The Irish Sun) with the highest circulation of any daily English-language newspaper in the world and the biggest circulation within the UK, standing at an average of 3,121,000 copies a day between January and June 2008 and with a daily readership of approximately 7,900,000, of which 56 percent are male and 44 percent female. By circulation it is the eighth biggest newspaper in any language in the world, one place behind its Sunday stablemate the News of the World, although their circulations are close and these places were briefly reversed during May 2008. It reaches 2.9 million readers in the ABC1 demographic and 5.0 million in the C2DE demographic, compared to the 1.5 and 0.1 million respectively of its broadsheet stablemate The Times. It is published by News Group Newspapers of News International, itself a subsidiary of Rupert Murdoch's News Corporation.

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 Press Corporation) to replace the failing Daily Herald. The name was acquired from the Student newspaper the SUN (Student University News) published by Aston University Student's Guild, with their newspaper being renamed the Birmingham SUN. The paper did not live up to IPC's expectations. Circulation continued to decline and it was soon losing even more money than the Herald had done. In 1969, IPC decided to throw in the towel. The tycoon Robert Maxwell, eager to buy a British newspaper (which he later did, with the Mirror Group in 1984) offered to take it off their hands and retain its commitment to the Labour party, but admitted there would be redundancies, especially among the printers. Rupert Murdoch had already bought the News of the World, a sensationalist Sunday newspaper, the previous year, but the presses in the basement of his building in London's Bouverie Street sat idle six days a week. Seizing the opportunity to increase his presence on Fleet Street, he made an agreement with the print unions, promising fewer redundancies if he got the paper. He assured IPC that he would publish a "straightforward, honest newspaper" which would continue to support Labour. IPC, under pressure from the unions, rejected Maxwell's offer, and Murdoch bought the paper for £800,000, to be paid in instalments. He would later remark: "I am constantly amazed at the ease with which I entered British newspapers."

Murdoch appointed Larry Lamb as his editor. Lamb was scathing in his opinion of the Mirror, the paper where he had recently been a senior sub-editor. He shared Murdoch's view that the measure of a paper's quality was best measured by its sales, and he regarded the Mirror as overstaffed, and primarily aimed at an aging readership. Lamb hastily recruited a staff of about 125 reporters, who were mostly selected for their availability rather than their ability. This was about a quarter of what the Mirror currently employed, and Murdoch had to draft in staff on loan from his Australian papers. Murdoch immediately relaunched The Sun as a tabloid, and ran it as a sister paper to the News of the World . The Sun used the same printing presses, and the two papers were now managed together at senior executive levels.