Optus will shut down its 2G network in April 2017, the telco revealed today.
"2G now constitutes a fraction of our total mobile network traffic and is declining significantly year on year," Optus Networks acting managing director Dennis Wong said in a statement.
"Mobile service providers globally, including in Australia and our parent company Singtel in Singapore, are closing down 2G networks to support newer technologies."
Optus' 2G network runs in the 900MHz spectrum.
"No decision has been made regarding the reallocation of spectrum," an Optus spokesperson told Computerworld.
"However it does provide us with an option to reallocate spectrum to improve customer experience and mobile services."
The move will also affect Virgin Mobile customers and MVNOs that rely on Optus Wholesale to provide services.
Telstra revealed last year that it would shut down its GSM network by the end of 2016.
Telstra's and Optus' 2G GSM networks both launched in 1993.
Telstra shut down its CDMA network in April 2008.
In May, Optus said it had 9.43 million mobile subscribers. Some 37 per cent of those — 3.53 million — are on the Optus 4G network.
As of the end of April, Optus' 4G network reached 86 per cent of Australia's population, according to the telco.
Optus' 4G network is supported by 3383 mobile sites; 2107 of those have been upgraded to support the 700MHz spectrum it won in 2013 Digital Dividend auction.