US President Donald Trump on Thursday ordered Lake Ontario to be renamed "Lake America" as he escalated his trade war with Canada, sparking immediate pushback from Ottawa.
Trump stepped up his trolling of Canada by signing an executive order changing the name of the body of water on the border between the North American neighbors.
But Canadian Prime Minister Mark Carney swiftly rejected Trump's move, saying it would be called Lake Ontario "then, now and always."
The volatile US leader's move comes after US-Canada trade talks collapsed at the last minute last week, prompting the two longtime allies to slap tit-for-tat tariffs on each other.
"We're going to be changing the name of Lake Ontario effective immediately to Lake America," the 80-year-old Republican told journalists as he signed the order at the White House.
Asked by an AFP reporter why he was targeting an ally for punishment instead of America's adversaries, Trump replied: "The Canadian officials have treated us very badly. They're nasty people."
Behind Trump's desk in the Oval Office were two maps -- one with the words "Lake America" in red over the lake, and the other with the header, "Making the Great Lakes Even Greater."
- Canada strikes back -
Lake Ontario is the smallest by surface area of the five Great Lakes, which straddle the border between the United States and Canada. It borders the Canadian province of Ontario and the US state of New York.
The name change mirrors Trump's unilateral altering of the name of the Gulf of Mexico to the Gulf of America in January 2025 -- a move Mexico has also rejected.
Carney retorted that the name of the lake was 400 years old -- predating the formation of both the United States and Canada -- and came from an Indigenous word meaning "the lake is beautiful, the lake is big."
"We know that America is changing," he said in a post on X.
"Canadians also know that naming reality means calling it Lake Ontario -- then, now and always."
Carney's defiance of Trump in recent days has won plaudits at home.
In Toronto, Canada's largest city which lies on the lake's northwestern shore, Canadians and Americans alike criticized Trump's move.
"Typical Trump. He's being a bully, he goads, he antagonizes," said Mark Weicker, who lives in Kitchener, west of Toronto.
"He's just trying to egg us on," chimed in Jake Marchuk, who was visiting from Alberta province.
- 'All we need is an ocean' -
Trump's executive order tells the US Department of the Interior to update references to the lake in the official geographical naming service within 30 days and ensure the federal government calls it "Lake America."
It justifies the name change by saying that the deepest part of the lake is on the American side, meaning that the United States "claims most of the Lake's volume."
Trump -- who faces low approval ratings amid the Iran war and economic woes at home, with crucial US midterm elections around the corner in November -- said he had been thinking about the name change "for a long time."
The US president even hinted at renaming oceans that border the United States.
"We have a gulf and we have a lake. Now all we need is an ocean. So, maybe we'll have to change the name of the Atlantic and/or the Pacific. Maybe we'll change them both," he said.
During his second presidential term, Trump has irked a series of allies with his outlandish territorial claims, including that Canada should become the 51st US state.
Trump has also laid claim to Greenland, an autonomous territory of NATO ally Denmark, and talked about making Venezuela a state following the US capture of its leader Nicolas Maduro.
In recent days, he has also said that he will make the Strait of Hormuz between Iran and Oman a US territory, despite the fact that the war with Tehran remains ongoing.
