Oi (then known as Telemar) was formed as Tele Norte Leste to merge sixteen state-owned incumbent local exchange carriers (ILECs), during the privatization of Brazilian telecommunications system. Each carrier served a particular Brazilian state in the northern, northeastern and southeastern part of the country. In the break-up of Telebras in 1998 it was sold to a consortium led by the Brazilian construction firm Andrade Gutierrez (21.2%) and Inepar Holdings (20%) as well as other Brazilian corporate and individual investors. The consortium paid 3.434 billion reais.
Initially, Telemar was allowed to offer only local voice and data services and interstate long distance voice services. Today, Telemar and its subsidiaries offer local, long distance and international voice and data services, besides a growing mobile phone network.
Currently, Oi has 22.2 million land lines in service, 31.7 million wireless customers, 4 million ADSL subscribers (2009) and about 44 thousand employees.
The states that formed the base of Telemar at its inception were Rio de Janeiro, Minas Gerais, Espírito Santo, Bahia, Sergipe, Alagoas, Pernambuco, Paraíba, Rio Grande do Norte, Piauí, Ceará, Maranhão, Pará, Amazonas, Amapá and Roraima, corresponding to 65% of the Brazilian territory and 20 million households.
Oi's stock is traded on Bovespa, where it is part of the Ibovespa index.
In April 2006, it was announced that Telemar would restructure itself, merging its three holding companies into a single company, that would have been named either Telemar Participações S.A. or Oi Participações S.A. However, those plans failed, since there was no consensus between Telemar shareholders. But on March 1, 2007, Telemar rebranded itself to "Oi", unifying all of its companies and services under the Oi umbrella. The company is still legally known as "Telemar Norte Leste S.A.", "Tele Norte Leste Participações S.A." and "Telemar Participações S.A.". Oi owns the brands:
* Oi Fixo (landline service, formerly Telefone Telemar)
* Oi Móvel (mobile service, the "original Oi")
* Oi Velox (ADSL, 3G formerly Velox)
* Oi Internet (ISP)
* 31 (long distance and international calling)
* Oi Voip (Voice over IP)
* Oi Wi-Fi (Wi-Fi access, at home or via hotspots)
* Oi TV (DTH pay TV)
* Brasil Telecom (to be phased out and replaced with Oi)
** iG (Internet service provider)
** iBest (to be absorbed into iG)
** BrTurbo (to be absorbed into iG)