Canada's Prime Minister Mark Carney has rejected US President Donald Trump's move to rename Lake Ontario "Lake America," saying Canadians will continue to use the lake's longstanding name.

"The name Lake Ontario comes from the Wendat word Ontari'io, which, appropriately, means 'the lake is beautiful, the lake is big'," Carney said on X on Thursday.

He noted that the name is more than 400 years old, predating both the Confederation of Canada and the Declaration of Independence of the US.

"We know that America is changing. Their trading relationships, their foreign policies, their national monuments, their hydronyms. Canadians also know that naming reality means calling it Lake Ontario – then, now and always."

His remarks came after Trump signed an executive order directing the renaming of Lake Ontario to "Lake America," amid trade tensions with Canada, saying the change would take effect immediately.

"We're going to be changing the name of Lake Ontario, effective immediately, to 'Lake America'," Trump said in the Oval Office before signing the executive order.

One of the five Great Lakes of North America, Lake Ontario borders both the Canadian province of Ontario and the US state of New York.

Relations deteriorated following the collapse of trade negotiations and Washington’s imposition of new tariffs on Canadian goods, with Ottawa quickly retaliating.