It comes after Donald Trump ordered the name to be changed amid an escalating trade war with Canada.
The Canadian province of Ontario is on the lake's north, west and southwest, while New York state is on its southern and eastern shore.
President Trump made a similar proclamation in 2025, saying the Gulf of Mexico should be known as the Gulf of America. Google now marks it as "Gulf of Mexico (Gulf of America)".
The company said the decision to retitle the lake was because the US government's Geographic Names Information System (GNIS) had now formally changed the name.
"People using Maps in the U.S will see 'Lake America,' those in Canada will continue to see 'Lake Ontario,' and those outside of the U.S. and Canada will see both names," Google said.
"These updates follow our long-standing policy for bodies of water with names that vary from country to country, and are starting to roll out now."
For UK users on Monday morning, it still appeared to be showing "Lake Ontario" only.
President Trump signed the executive order to rename the lake on Thursday and suggested he might not be done.
He told reporters at the White House: "If you think about it, 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."
The move to rename the lake was - unsurprisingly - met with derision in Canada.
Canadian Prime Minister Mark Carney responded on X: "The name Lake Ontario comes from the Wendat word Ontari'io, which, appropriately, means 'the lake is beautiful, the lake is big'.
"The name is more than 400 years old, predating both the Confederation of Canada and the Declaration of Independence of the United States of America."
Read more from Sky News:
Meet the unit of Russia defector fighting for Ukraine
At least eight dead after ferry capsizes off northern Cyprus
The relationship between the countries' governments is going through another bumpy patch after trade disagreements flared up again.
Mr Trump imposed a 50% tariff on $20bn of Canadian imports this month, prompting Canada to retaliate "dollar for dollar" with an equal amount of tax on a range of US goods.
The Met Police described the mood as "overwhelmingly positive", despite making 169 arrests on Sunday.
In a statement, the force said: "While officers responded to a number of incidents as would be anticipated at an event of this scale, the mood has been overwhelmingly positive and celebratory."
It said, as of 7.45pm on Sunday, the arrests had been made for offences including possession of drugs, possession of weapons, assaults and sexual offences.
In 2025 the Met said it made 528 arrests across the two main days of the carnival, and in 2024 there were eight stabbings, including the murder of 32-year-old mother Cher Maximen.
Commander Claire Smart, who is in charge of the policing operation, said: "While we have seen a significant number of arrests and interventions by officers, the result of that proactive approach is a welcome reduction in the levels of serious violence seen at the event in previous years.
"Nobody involved in the delivery of the event is complacent, however.
"There are still many officers deployed across the footprint to ensure crowds disperse safely.
"We will have officers on duty through the night and tomorrow we will go again to ensure we can continue to tackle the minority who want to come to carnival to spoil the celebration for the majority."
Read more from Sky News:
PM's pledge to end 'injustice' of IPP sentences
Man killed at Christian festival named
Earlier this week, the force said more than 7,000 officers would be deployed to west London over the bank holiday weekend.
Facial recognition is also being used again this year.
The celebration of Caribbean culture, which is marking its 60th anniversary this year, includes parades, live music, street food and sound stages.
Police were called to an address in the Wincobank area of Sheffield just before 6am on Sunday over concerns for the safety of a newborn.
Officers searched a property on Holywell Heights, where the baby was found. The infant was pronounced dead at the scene, despite the best efforts of officers and paramedics, South Yorkshire Police said.
Read more from Sky News:
Man killed at Christian festival named
Two missing after fishing boat sinks
Detective Chief Inspector Emma Knight said: "We are aware news of this will be deeply concerning and I want to reassure our local communities that we have a dedicated team of detectives and officers hard at work to ensure justice is secured for the baby girl at the heart of this investigation.
"As part of our investigation, seven people have been arrested on suspicion of murder. All of them remain in police custody at this time. We are working to determine the ages of some of those arrested.
"Our investigation is in its early stages, and we would like to remind people to avoid speculating about this incident."
Police have urged anyone with information over the incident to contact them, either directly or through Crimestoppers.
PC Matthew Blades, described by the club as a "proud Red", was killed in a collision with a vehicle going the wrong way down the A66 last weekend.
The vehicle that struck his had been involved in a police pursuit shortly before, but officers broke off the chase. Mr Blades' colleague PC Tom Clough also died in the collision.
The club expressed "great sadness" at the death of the two PCs and invited Mr Blades' wife and two sons to their Premier League match against Ipswich at Old Trafford.
Walking with captain Bruno Fernandes and goalkeeper Senne Lammens, the children led out the team onto the pitch as mascots.
Manchester United said in a statement: "Matthew was a proud Red, a devoted family man and a police officer who dedicated his life to helping others.
"For Matt, some of his happiest times were spent watching United with his boys."
On Saturday, Middlesbrough paid tribute to the pair and other Cleveland Police officers, holding a minute's silence before their match with West Bromich Albion.
Manchester United also published a tribute from an unnamed friend and colleague of PC Blades in their programme on Sunday.
It read: "For Matthew, United was a lifelong love, a passion he shared with his family.
"Since Matt's tragic death there has been an extraordinary outpouring of grief and support. That love has been seen in countless tributes and acts of kindness.
"Today, we remember a fellow Red. A husband. A father. A son. A brother. A friend. A police officer. A man who gave his life in the service of others. Forever our superhero."
Three others were rescued after the Maritime and Coastguard Agency (MCA) was alerted that the vessel, with five people on board, was "in distress" off the coast of Plymouth, Devon, just after 6pm on Saturday.
The vessel was believed to have been in trouble southwest of Eddystone Lighthouse, which is 15 miles south of Plymouth.
The MCA said a rescue operation was launched, with a coastguard helicopter, a fixed-wing aircraft, and RNLI lifeboats from Falmouth and Plymouth scrambled to the area.
The French Navy's Falcon 50 was also deployed to assist.
Those rescued were taken to hospital, but the agency said on Sunday night that the search for the two remaining crew members had been "suspended pending further information".
In an earlier statement, the coastguard said: "Three people were rescued last evening from the French-registered fishing vessel which had made the call for help. They were taken to hospital for further care."
The statement added: "The vessel has sunk."