Telefónica in the context of Vivo (telecommunications company)

O2 (typeset as O₂) is a British brand owned by Spanish telecommunications company Telefónica, used for its subsidiaries in the United Kingdom and Germany, its former subsidiaries in the Czech Republic and Slovakia, and since 2018 as an online-only flanker brand in Spain. The O2 brand was created by British Telecom (BT) in 2001 ahead of the demerger of its global BT Wireless division as mmO2 plc (later O2 plc).

BT Wireless provided telecommunications services in the United Kingdom (BT Cellnet), Ireland (Digifone), Germany (VIAG Interkom), the Netherlands (Telfort), the Isle of Man (Manx Telecom), and a global mobile data business known as Genie Internet. Most of these operations were rebranded as O2 following the demerger from BT. In 2006, O2 plc was acquired by Telefónica, becoming Telefónica Europe. As part of a reorganisation of Telefónica in 2014, Telefónica Europe's holdings and operations became direct subsidiaries of its parent: Telefónica S.A.

O2 Czech Republic (operating under the O₂ brand) is a major integrated operator in the Czech Republic. It is now operating more than six million lines, both fixed and mobile, making it one of the Czech Republic's largest providers of fully converged services. O2 Czech Republic operates a fixed and mobile network including a 3rd generation network, CDMA (for data), UMTS and EDGE, enabling voice, data and video transmission. O2 Czech Republic is also a provider of ICT services.

Previously two companies, fixed-line operator Český Telecom and mobile operator Eurotel, it was acquired by the Spanish company Telefónica in 2005 and merged into a single legal entity and given its present name on 1 July 2006.

Telefónica Ireland was a broadband and telecommunications provider in Ireland that traded under the O2 brand (typeset as O₂). O2 Ireland was previously called Esat Digifone when it was owned by Esat Telecommunications (and Telenor) from 1997 to 2006.

O2 Ireland became a subsidiary of Telefónica in 2006, after its parent company O2 in the United Kingdom was purchased. In June 2013, Hutchison Whampoa announced it would acquire the Irish arm of O2 for €780 million. O2 was merged into Hutchison Whampoa's subsidiary Three Ireland in March 2015.

Virgin Media Limited is a British telecommunications company which provides telephone, television and internet services in the United Kingdom. Its headquarters are at Green Park in Reading. It is owned by Virgin Media O2, a 50:50 joint venture between Liberty Global and Telefónica. Since its foundation in 2007, the company has used the Virgin branding under license from Richard Branson.

Virgin Media owns and operates its own hybrid fibre-coaxial and fibre to the premises (FTTP) networks. Although most of the network is urban, Nexfibre (a 50:50 joint venture between Virgin Media O2 and Infravia Capital Partners) is expanding the network to more areas. As of year end 2024, it had a total of approximately 5.8 million customers. Since the acquisition of Smallworld Cable in 2014, Virgin Media is the main cable provider in the UK, with connections available to over 18.4 million homes in 2024. Virgin Media is one of the "big four" internet service providers in the UK along with BT (EE), Sky and TalkTalk. In the past, Virgin Media also operated a mobile virtual network operator (Virgin Mobile) and operated TV channels and produced television content (Virgin Media Television).

Virgin TV is a digital pay cable television service in the United Kingdom, owned by Liberty Global (50%) and Telefónica (50%) after the merger its UK businesses to form Virgin Media O2. Its origins date from NTL and Telewest, formerly two of the UK's largest cable operators, which merged on 6 March 2006. All NTL:Telewest services were rebranded as Virgin Media in February 2007. Since the acquisition of Smallworld Cable in 2014, Virgin is the sole national cable TV provider in Great Britain. Currently about 51% of UK households have access to Virgin's network, which is independent from BT's Openreach network.

Virgin ranks as the UK's second-largest pay TV service, and the service is provided in conjunction with Virgin Media broadband and phone. As of Q3 2007, it had 3.6 million subscribers, compared to 8.2 million on its traditional rival Sky. As of 2009, Virgin's digital cable television currently uses the Nagravision 3 conditional access system. The service was fully digitalised in 2013.