Events are being held across the world to mark the 80th anniversary of Victory in Europe Day.
Britain's King Charles and Prince William laid wreaths in Westminster Abbey at the culmination of the UK's four days of commemorations.
The thanksgiving service in the Abbey began with a two-minute silence, which was also observed across the UK, to remember Nazi Germany's unconditional surrender at the end of World War II, which took effect on 8 May 1945.
Charles and William, military medals pinned on their chest and standing beside elderly veterans in wheelchairs, laid wreaths at the Grave of the Unknown Warrior, in a show of respect for those who gave their lives in World War II.
The anniversary, which comes at a time of ongoing conflict in Europe with Russia's war in Ukraine, was also marked with events in France and Germany, while Moscow will hold a major military parade tomorrow.
Speaking at a defence conference in London, British Prime Minister Keir Starmer called the day a celebration of defiance, sacrifice and courage.
"A victory not just for Britain but for good against the assembled forces of hatred, tyranny and evil," he said.
In Moscow, Russian President Vladimir Putin spoke of the "sacred" victory over Adolf Hitler and said his country was standing against "neo-Nazism", a characterisation of the current conflict in Ukraine that is strongly rejected by Kyiv.
Mr Putin was holding talks with Chinese President Xi Jinping, who is joining Russia's celebrations.
French President Emmanuel Macron was due to lay a wreath at the statue of French wartime hero Charles de Gaulle in Paris and inspect a troop parade at the Arc de Triomphe. Dozens of World War II-era vehicles will also parade down the Champs-Elysees avenue.
In Berlin, President Frank-Walter Steinmeier will address the Bundestag, the lower house of Germany's parliament, during a special remembrance session.
VE Day's 80th anniversary will be one of the last major celebrations with living veterans attending events, as most are now in their 90s or older.
British veterans were among the congregation at Westminster Abbey in London. They will be greeted by Charles and his wife Queen Camilla after the service, before senior royals also lay flowers at a memorial nearby.
Veterans also attended a grand military parade and fly past close to Buckingham Palace on Monday, one of a series of anniversary events.
Later, there will be a concert at Horse Guards Parade for 10,000 people. Charles and Camilla will be in the audience to hear music and the stories of veterans.
VE Day marked with events across Ireland
A ceremony to remember the thousands of Irish soldiers who fought and died in World War II was held at the Irish National War Memorial Gardens in Islandbridge in Dublin.
Those gathered held a minute's silence at noon, before being addressed by Chairman of the Royal British Legion in the Republic of Ireland Paul Stephenson.
"As we celebrate the triumph of liberty over oppression, we must also pause to reflect on the immense cost of victory, over 70 million lives were lost during this global conflict, each one a unique story, a precious existence extinguished too soon," Mr Stephenson said.
"Among them were up to 10,000 Irish men and women who made the ultimate sacrifice. They came from towns and villages across Ireland stepping forward with courage to serve with the armed forces as nurses, medics, auxiliary support and in countless other roles.
"Their bravery was not just in their actions but in their willingness to fight for a cause greater than themselves," Mr Stephenson said.
Jim Kearns of the Dublin Central Branch Royal British Legion committee then laid a poppy wreath at the foot of the Garden's War Stone, which bears the inscription "Their Name Liveth for Evermore".
Ireland maintained a policy of neutrality during World War II.
Mr Stephenson said that many of those who came back from serving with the allied forces kept their participation in the war effort quiet.
"My own uncle was in the Second World War, but it was never spoken about and I used to visit his house and there was a photograph of him in uniform in Normandy and he never mentioned it," Mr Stephenson said.
"A lot of people didn't speak about, and it was the same with the First World War, people came back and didn't speak about it."
Secretary of State for Northern Ireland Hilary Benn described an opportunity to remember the "huge sacrifice made by that great generation" at the end of World War II in Europe.
Last night, some landmark buildings in Belfast were lit up to mark VE Day, including Belfast City Hall in red, as well as Parliament Buildings in blue.
Later today, beacons will be lit across a number of locations including Bangor, Newtownards, Lisburn, Armagh, Enniskillen, Coleraine, Derry and Coleraine.
Mr Benn took part in a number of visits across the region.
He officially opened a special World War II exhibition at Antrim Castle Gardens, before travelling to the Ulster Aviation Society, where he met veteran Fred Jennings.
Additional reporting by Laura Fletcher
