O2 (typeset as O2) is a global brand name owned by the Spanish telecommunications company Telefónica. The company uses the O2 brand for its subsidiaries in the United Kingdom and Germany. Since 2018, it is also used as an online-only flanker brand in Spain.Formerly, all European branches of Telefónica were managed by Telefónica Europe plc, a broadband and telecommunications company. The company originated as a collection of worldwide telecommunications companies, known in the later half of the 1990s as BT Wireless, and a global mobile data business known then as Genie Internet, both subsidiaries of British Telecommunications. As part of a reorganisation of Telefónica in 2014, Telefónica Europe's holdings and operations became direct subsidiaries of its parent: Telefónica S.A.Telefónica Europe provided mobile telephony operations in the United Kingdom and Germany, and licensed its brand to former operations in Ireland, the Czech Republic, and Slovakia. O2 has additionally established a joint venture with Tesco Mobile in the United Kingdom, Ireland and in Slovakia, and the Tchibo Mobilfunk network in Germany.

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