The GBU-43/B Massive Ordnance Air Blast Bomb (MOAB), known as "the mother of all bombs", is the largest non-nuclear bomb ever used by the US in a conflict. It is more than 9m (30 feet) in length.
It was first tested in 2003, but had not been deployed in combat before.
The Pentagon said it was dropped in Achin district on Thursday evening local time from a US aircraft in Nangarhar province.
The news came hours after the Pentagon admitted an air strike in Syria mistakenly killed 18 rebels.
It said a partnered force had mistakenly identified the target location as an IS position, but the strike on 11 April had killed rebels from the Syrian Democratic Forces, which is backed by Washington.
(Excerpts : BBC News)