Barack Obama has banned oil and gas drilling in large areas of the Arctic and the Atlantic Ocean.
The President enacted a 1953 law called the Outer Continental Shelf Lands Act to make than 100 million acres off-limits for fossil fuel exploration.
He co-ordinated the move with Canadian Prime Minister Justin Trudeau to also shield large areas of Canadian waters.
Neither measure will affect any existing contracts or leases.
A White House statement said: “These actions and Canada’s parallel actions protect a sensitive and unique ecosystem that is unlike any other region on earth.
“They reflect the scientific assessment that, even with the high safety standards that both our countries have put in place, the risks of an oil spill in this region are significant and our ability to clean up from a spill in the region’s harsh conditions is limited.”
A number of green groups have suggested that Donald Trump may need to take the case to court if he wants to undo the action.