Mr O’Sullivan will succeed Oonah McPhillips, who is retiring after a 41-year career, with effect from Monday 20 April 2026.

Justice, home affairs and migration minister Jim O’Callaghan said: “I am very pleased that government has today appointed Doncha O’Sullivan as secretary general of the Department of Justice.

“Doncha has dedicated his career to the work of this department and the wider justice sector and is strongly placed to lead the department in the coming years.

“As deputy secretary general for civil justice, including immigration, he has led the development of strategy and reform across the sector, promoting access to justice and progressing the government’s legislative programme.

“He has overseen key policy and legislative measures in relation to immigration, working closely with partners across government and wider stakeholder groups.

“His leadership and experience will be invaluable as we continue to deliver on our ambitious programme of work.

“I look forward to continuing to work with Doncha in his new role and wish him every success.”

In addition to his role as deputy secretary for civil justice, Mr O’Sullivan’s career in the Department of Justice has included senior management roles as head of corporate and of civil justice governance. He has also worked across criminal policy, policing, prisons and EU affairs.

He holds an MEconSc (IPA/Trinity), a BA in Law (DIT), and a BA in Economics and History (UCC). He grew up in Cork City.

Mr O’Callagan added: “I want to take this opportunity to commend Oonagh’s strong leadership and exemplary commitment to the Department, which she has demonstrated over her many years of dedicated public service.

“Oonagh became secretary general during a key period following a significant restructuring within the Department.

“Based on the extensive experience and expertise developed during her long career within the justice sector, she has focused throughout her term as secretary general on further strengthening the capacity of the Department to deliver, across the breadth of its responsibilities, on its vision for a safe, fair and inclusive Ireland.

“Oonagh has prioritised, throughout her career, the interests of the people of this country, truly embodying the spirit of public service. I wish her all the best for the future in her retirement.”