"Coalition forces targeted Rachid Kassim, a senior ISIS operative, near Mosul in a strike in the past 72 hours," US Maj. Adrian Rankine-Galloway said.
The Pentagon said it is still assessing the results, but a senior US defense official told CNN that it was "likely successful."
The official added that the airstrike was carried out by a drone.
Kassim is a French citizen who has allegedly inspired terrorist attacks in France. He is considered one of the most dangerous of all ISIS operatives because he enabled a string of plots against France by communicating with ISIS sympathizers in France through encrypted messaging apps.
Kassim encouraged and guided plotters to launch attacks, even bringing together individuals who did not know each other to form attack cells. French intelligence agencies believe he was in touch with the attacker who killed a French police couple in northwestern France in June and the two plotters who killed a priest in Normandy in July.
More then half of the 17 foiled plots against France in 2016 were guided by Kassim, according to Jean-Charles Brisard, the director of the Paris-based Center for the Analysis of Terrorism.
"Kassim is the single most active French remote attack planner for ISIS, working to drive dozens of radicalized individuals in France to commit attacks," Brisard told CNN.
Social media reports seemed to indicate that Kassim was killed, Brisard said.
In the past 24 hours, several Telegram channels belonging to French ISIS operatives asked followers to pray for Kassim and his family "pending news that will strengthen your hearts," Brisard said.
Brisard said that in the past, such messages have been posted when operatives have been killed, but he stressed the importance of Western intelligence agencies confirming the death because of the possibility ISIS might try to fool Western intelligence into concluding that Kassim is dead.
Mosul is the site of pitched battles between Iraqi forces -- aided by coalition forces -- and ISIS, which seized control of the large city in 2014. The coalition recently wrested the parts of the city east of the Tigris River from ISIS control. Officials have said the fight for control of the west side could drag into March.