The former head of Germany's war crimes unit has been chosen to lead the UN body investigating atrocities carried out against the Yazidi minority by ISIS.
Christian Ritscher will replace British lawyer Karim Khan as the head of Unitad.
Mr Ritscher was appointed by UN Secretary General Antonio Guterres to take over the unit, which has been running since 2017.
It is working to hold ISIS accountable for its genocidal campaign against the Yazidi community. ISIS terrorists massacred thousands of Yazidi men and older women, took boys to train as child soldiers and abducted girls to be used as sex slaves.
Mr Khan left Unitad in June to take up the role of chief prosecutor at the International Criminal Court.
Mr Ritscher previously served as a federal public prosecutor in Germany and has more than 30 years of professional experience in international and domestic prosecutions and investigations.
He was head of Germany's S4 war crimes unit. This is responsible for the prosecution of people for crimes that may have been committed elsewhere, including in Iraq and Syria.
It prosecuted members of ISIS for crimes committed against the Yazidi community in Iraq in 2014. It also charged other suspects with international offences.
The Free Yazidi Foundation, a campaign group, welcomed his appointment.
"Mr Ritscher is a serious prosecutor who has already focused great energy on building cases in court," it said.
"We look forward to continued co-operation."
Under Mr Khan's tenure, the first remains from Yazidi mass graves in Iraq were exhumed. Some families got to bury their loved ones after a six-year wait.
Mr Khan wished his successor good luck in the role.
Unitad is hoping to begin its first prosecutions this year, using evidence uncovered in the mass burial sites.
More than 200 mass graves containing about 12,000 victims have been identified, revealing the scale of the ISIS campaign against the Yazidi people.
The UN team has now found evidence linking more than 350 ISIS fighters to the war crimes.
Using more than two million pieces of data from mobile phones, investigators were able to place ISIS members at the scenes of the atrocities.
The unit has been training Iraqi investigative judges in developing case files for the prosecution of ISIS members for war crimes, crimes against humanity and genocide.