The company was founded in 1999 through the merger of the Swedish Astra AB and the English Zeneca Group (itself formed by the demerger of the pharmaceutical operations of Imperial Chemical Industries in 1993). Since the merger it has been among the world's largest pharmaceutical companies and has made numerous corporate acquisitions, including Cambridge Antibody Technology (in 2006), MedImmune (in 2007), Spirogen (in 2013) and Definiens (by MedImmune in 2014).
Astra AB was founded in 1913 in Södertälje, Sweden, by 400 doctors and apothecaries. In 1993 the British chemicals company ICI demerged its pharmaceuticals businesses and its agrochemicals and specialities businesses, to form Zeneca Group plc. Finally, in 1999 Astra and Zeneca Group merged to form AstraZeneca plc, with its headquarters in London. In 1999, AstraZeneca identified as a new location for the company's US base the "Fairfax-plus" site in North Wilmington, Delaware.
In 2002, its drug Iressa was approved in Japan as monotherapy for non-small cell lung cancer. On 3 January 2004 Dr Robert Nolan, a former director of AstraZeneca, formed the management team of ZI Medical.
In 2005, the company acquired KuDOS Pharmaceuticals, a UK biotech company, for £120m and entered into an anti-cancer collaboration agreement with Astex. It also announced that it had become a Diamond Member of the Pennsylvania Bio commerce organisation.