Optus boss Kelly Bayer Rosmarin has resigned after the telecommunications giant suffered a fraught 18 months marked by a cyber attack and an hours-long outage that affected millions of Australians.
Ms Bayer Rosmarin tendered her resignation on Monday.
"It's been an honour and privilege to lead the team at Optus and to serve our customers," she said.
"I was also able to communicate Optus' commitment to restore trust and continue to serve customers.
"Having now had time for some personal reflection, I have come to the decision that my resignation is in the best interest of Optus moving forward."
Chief financial officer Michael Venter will be interim CEO while continuing in his current position.
Former Optus business managing director Peter Kaliaropoulos will become the company's chief operating officer from Wednesday, a new position that reports to Mr Venter.
Prime Minister Anthony Albanese lambasted the telco on Monday, calling the outage and Optus's response "a really regrettable incident".
"Many individuals, millions of Australians and so many businesses were left without information about what was going on," he told Sky News.
The government was working on an analysis that would draw lessons from the outage and send a message to the public and private sectors, he said.
Communications Minister Michelle Rowland said it was undoubtedly a difficult decision and she wished the former CEO well for the future.
"We need to learn the lessons to ensure industry and government is as prepared as possible, given no network is fully immune," she said.
Ms Bayer Rosmarin was appointed to the top job in April 2020, during the height of the COVID-19 pandemic.
In September 2022, she presided over one of the telco's worst PR disasters when it suffered a massive data breach that affected 10 million Australians and resulted in the driver's licence, Medicare and passport numbers of 10,000 customers being stolen and leaked online.
About 14 months later, Optus was hit by a 12-hour-long outage that prevented more than one-third of Australians from accessing the internet and receiving cell service.
More than 200 emergency calls could not go through to the triple-zero line.
Yuen Kuan Moon, chief of Optus's parent company Singtel, acknowledged the former CEO's leadership.
"Kelly has always led with integrity and had all stakeholders' best interests at heart," he said.
"We understand her decision and wish her the very best in her future endeavours."
Following the November 8 outage, Ms Bayer Rosmarin was summoned to a parliamentary inquiry where she was roasted by senators channelling the ire of their constituents.
During Friday's hearing, Nationals senator Ross Cadell queried her response during and after the network shutdown and asked whether it was time for new leadership at the telco.
She said she would "take that on board".
Greens senator Sarah Hanson-Young, who chairs the Senate inquiry into the outage, thanked Ms Bayer Rosmarin for answering questions.
"This was never about which individual is CEO," Senator Hanson-Young said.
"This is about ensuring millions of Australians have access to what is an essential service, including the ability to call 000 in an emergency, access government services, contact loved ones and make and take essential payments."
The Senate inquiry would continue examining solutions, such as stronger regulations for telecommunications companies, Senator Hanson-Young said.
Opposition communications spokesman David Coleman said Ms Bayer Rosmarin's resignation was not surprising.
"The focus must now turn to investigating what went wrong, especially with regards to the 000 calls that did not get through," he said.
The government announced a review of the network outage nearly two weeks ago.
Australian Associated Press