The official name of this brand is O2, as displayed above. The substitution or omission of the subindex in the URL is due to technical restrictions.

O2 (stylised as O2) is one of three consumer brands used by the Spanish telecommunications company Telefónica, the others being Movistar, used in Spain and Spanish American countries, and Vivo, used in Brazil. Telefónica acquired the O2 mobile networks in 2005–2006. Telefónica-owned O2 networks operate in the following countries:

The O2 brand is licensed to the Czech investment company PPF Group for use in the following countries (Telefónica owned the networks until 2013):

Furthermore, O2 also operated in Ireland until Hutchison Whampoa acquired it in 2015 and discontinued the O2 brand in favour of its own Three brand.

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