Stephanie Foster will take over as secretary of the Department of Home Affairs, succeeding Mike Pezzullo, whose near-decade long stint in the top job ended abruptly on Monday.
Ms Foster was rumoured to be in pole position for the role, as the acting secretary, and the second-most senior public servant in the department.
She had been acting in the role since September, when Mr Pezzullo agreed to stand aside following allegations he had sought to wield political influence.
He was fired on Monday, when an inquiry led by former Public Service Commissioner Lynelle Briggs found he breached the APS Code of Conduct 14 times.
Prime Minister Anthony Albanese announced late on Tuesday afternoon that Ms Foster would commence as department secretary for a standard term of five years.
The appointment happened at speed for the federal public service - where top jobs can take months to be filled - but is understood to have followed standard process, including a report from the Prime Minister and Cabinet secretary Glyn Davis.
"Ms Foster has had an extensive career in the Australian Public Service," Mr Albanese said, referencing her time in Home Affairs and Prime Minister and Cabinet.
"[She] has held other senior positions in the APS, including at the Australian Public Service Commission, the Department of Infrastructure and the Department of Defence," the Prime Minister said.
"Ms Foster has well-established relationships across the APS and significant policy experience, which make her eminently suitable to the role of Secretary."
Ms Foster began in the Department of Home Affairs as associate secretary of immigration in October 2022, after moving across from a deputy secretary role in Prime Minister and Cabinet.
She is a career public servant, who began in the Defence Signals Directorate - now the Australian Signals Directorate - in 1987 as a graduate.
The new secretary is understood to have a good relationship with Home Affairs Minister Clare O'Neil, and a "great reputation" in the public service.
"She is very capable in terms of understanding how the public service works," said Abul Rizvi, a former deputy secretary in the Department of Immigration until 2007.
"She's very good at managing ministers, she's a very diligent public servant."
Speculation about who would take over as secretary of the department had already begun on Monday, when Mr Pezzullo's termination was announced.
While Ms Foster was thought to be a strong contender, there was also speculation that an existing departmental head, such as Department of Social Services boss Ray Griggs, could put up their hand.
Foster takes on role amid intensifying scrutiny of Home Affairs
The appointment comes at a fraught time for the Albanese government, which is facing intensifying pressure from the Coalition over its response to a High Court ruling that indefinite immigration detention was unlawful.
Opposition spokesperson for home affairs James Paterson focused on the issue, when asked about who should fill the secretary role, earlier on Tuesday afternoon: "I don't have a view about suitability of people for public service appointments, that's really something only the government can do," he said.
"What we want to see from the government at the political level is leadership to make sure that next time they get surprised by a High Court decision, they're ready and that doesn't rest on public servants.
"It really rests on ministers to instruct their departments to be ready and to act quickly when decisions like this are handed down."
The Albanese government denies it did not act swiftly enough to respond to the ruling, after rushing through emergency legislation earlier this month.
Ms Foster will also be tasked with overseeing reforms to the immigration system introduced by the government this year.
"Fixing the immigration mess, as the Minister has described it, is a really, really long, torturous and difficult task," Mr Rizvi said.
"Stephanie is more than capable of doing that, but she would need support from people with more corporate knowledge of the immigration issues than she has available to her at the moment."