The Pentagon said all military targets on the island were destroyed.
Kharg, which covers around 20 square kilometres, hosts Iran's main oil storage and loading facilities.
Around 80 percent of the country's crude oil exports pass through the island's terminals.
Iranian authorities had previously stated that any attack on Kharg would constitute a "red line".
Tehran has warned that destruction of its oil infrastructure would prompt retaliatory strikes against refineries elsewhere in the region.
Satellite imagery of the island, analysed since the start of the conflict, suggests Iran may have already emptied its oil storage tanks there.
The strikes have drawn mixed reactions.
Some commentators have questioned the delay in targeting the island; others have noted Iran's repeated warnings about escalation in the event of such an attack.
(ał)
Source: IAR