Iran's state-run press television said the US-made RQ-4 Global Hawk was shot down in the country's southern coastal Hormozgan province, near the Hormuz Strait.
CNN cannot independently verify the details of the Iranian state media report.
Press TV-cited Cap. Bill Urban, a spokesman for the US Central Command, said "no US aircraft operated in Iranian airspace" Thursday. CNN has reached the Pentagon for comment.
US officials owe Iran to attack oil tankers in Oman Bay, and the US president himself told Iran last week to be behind the provocation and tell Fox News: "They were the ones who did it."
Iran has previously been charged with targeting American drones.
It can fly more than 30 hours at a height of 60,000 feet (about 18,000 meters) and with a range of 12,300 miles.
Since 2001, Gobal Hawk became a member of the US Air Force fleet. It has collected more than 250,000 flight hours in support of military operations in Iraq, Afghanistan, North Africa and the Asia-Pacific.