Abdul Rahman Mustafa al-Qaduli, an Iraqi also known as Hajji Iman, died during a raid by US special forces on Thursday, officials told NBC News.
US Defence Secretary Ash Carter was expected to confirm the jihadist’s death and provide details of the raid in a statement at 14:30 GMT.
The US authorities had offered a reward of $7m (£5m) for Qaduli.
Qaduli, an ethnic Turkmen, was born in 1957 or 1959 in the northern Iraqi city of Mosul, which has been controlled by IS since 2014.
He joined al-Qaeda in Iraq (AQI) – a precursor of IS – in 2004 under the leadership of the late Abu Musab al-Zarqawi, serving as his deputy and the local leader in Mosul, according to the US.
After his release from an Iraqi prison in early 2012, he joined IS forces in Syria. READ MORE OF THIS STORY