Jon Boutcher has been formally appointed as interim chief constable of the Police Service of Northern Ireland (PSNI).
He takes over from Simon Byrne who quit in September after a series of crises under his leadership.
Mr Boutcher has decades of experience within policing and is a former chief of Bedfordshire Police.
The appointment was confirmed by Northern Ireland Secretary Chris Heaton-Harris.
Earlier this month, Mr Boutcher had been selected to be the PSNI's interim leader, but his appointment was subject to agreement.
Policing Board chair Deirdre Toner said Mr Boutcher's appointment will bring stability to the PSNI and the executive leadership team until a recruitment process for a permanent leader is complete.
"The board looks forward to working with Mr Boutcher and the wider service executive team as we progress the issues and pressures currently facing policing," she added.
Mr Boutcher said that he was "absolutely delighted to be given the privilege of leading the exceptional men and women of the PSNI".
He said that he is "aware of the challenges the organisation faces" and "how distracting and frustrating recent events have been".
Mr Boutcher said that the PSNI needs a "period of stability", and said his first job would be to gain the confidence of rank-and-file officers within the force.
Applications are currently open for the permanent chief constable role on a salary of almost £220,000, however, it will be several months before they would start the job.
The closing date is noon on 16 October.
Mr Boutcher would not comment on whether he would be applying to take on the role of chief constable on a permanent basis.
The Northern Ireland Secretary, Chris Heaton-Harris, said he welcomed the interim appointment.
"I congratulate the Northern Ireland Policing Board on moving swiftly in order to ensure the PSNI has the leadership and operational resilience it requires at this time," he said.
The PSNI has been without a chief constable for several weeks after Mr Byrne's resignation.
He quit in the wake of a court ruling that determined that two junior police officers had been unlawfully disciplined after making an arrest at a Troubles commemoration event in Belfast.
The previous month the force had mistakenly shared the identities of its entire workforce online in what was described by senior officers as a "major data breach".
Rank-and-file officers subsequently passed a vote of no confidence in some of the PSNI's other senior leaders.
Who is Jon Boutcher?
This wouldn't be Mr Boutcher's first time in a force's top job, previously leading Bedfordshire Police.
He spent the past five years overseeing an independent investigation into the activities of the Army's top spy within the IRA during the Troubles in Northern Ireland.
His Operation Kenova report into the agent, who was known as Stakeknife, is due to be published in the coming months.
Sir Iain Livingstone, a former chief constable of Police Scotland, will take over from Mr Boutcher in leading operation Kenova.
Mr Boutcher said that his taking the role of interim chief constable of the PSNI should in "no way" delay the publishing of the Kenova report.
He had previously applied to lead the Metropolitan Police after the resignation of Cressida Dick last year, but he was unsuccessful in that process.
He was also unsuccessful in his bid to become PSNI chief constable in 2019, when the job went to Mr Byrne.
