The informer, a man of unknown nationality, provided detailed information about Abu Bakr al-Baghdadi's final hideout, the Daily Mail reported, citing a US daily.
During the US operation, a "well-placed mole", who was present inside Baghdadi's Syrian compound, gave the precise interior layout as well as Baghdadi's exact location.
Syrian Democratic Forces (SFD) General Mazloum Abdi said that the informer described a room-by-room layout of the terror leader's compound on the Turkish border, including the number of guards, floor plan and tunnels, the UK news website reported, citing NBC News.
The IS insider is likely to receive some or all of the $25 million bounty that the US had placed on Baghdadi.
He is believed to be the same individual who gave US intelligence a pair of Baghdadi's used underwear and a blood sample at some point this year.
During the operation, US soldiers used the DNA from those samples to positively identify Baghdadi from the remains found in the compound after the suicide blast, that killed him and his three children on Saturday last week.
Announcing the death of Baghdadi on Sunday, Trump said Baghdadi died "after running into a dead-end tunnel, whimpering and crying and screaming" during a raid by the US forces in northwestern Syria.
"He reached the end of the tunnel, as our dogs chased him down. He ignited his vest, killing himself and three children. His body was mutilated by the blast," Trump said.
( With inputs from IANS )