Telefónica Germany was founded in 1995 as Viag Interkom, as a joint venture between British Telecommunications , VIAG and Telenor . Viag Interkom was awarded Germany's second GSM-1800 license in February 1997 and began operations on 1 February 1998 in eight cities.
In 2001, BT acquired VIAGs remaining shares for €11.4 billion, and the company was renamed BT Germany, it became a part of BT Wireless, a group of subsidiary companies owned by BT. BT Wireless demerged from BT in 2001 to form mmO2 plc and Viag Interkom was relaunched as O2 Germany.
In 2005, mmO2 plc. of which O2 Germany is a part, was acquired by Spanish telecoms giant, Telefónica. O2 Germany rebranded as Telefónica O2 Germany GmbH.
In 2011, Telefónica O2 Germany merged with HanseNet and renamed the merged company to Telefónica Germany.
In September 2014, Telefónica Germany announced the sale of €3.62 billion in new stock to help finance the acquisition of its competitor E-Plus from KPN. As part of the purchase, Telefónica reduced its stake in its subsidiary to 62.1%.In June 2020, Telefónica announced the sale of 10,100 mobile sites to Telxius for € 1.5 billion.
