Major Ollie Plunket of the Rifles, equerry to the Queen, laid a wreath on her behalf.
Wreaths were also placed by Sir Keir Starmer, Kemi Badenoch and Sir Ed Davey, as well as representatives of Plaid Cymru, the DUP and the speaker of the House of Commons.
After the two-minute silence at 11am and the laying of wreaths, the march-past organised by the Royal British Legion began at about 11.45am.
About 10,000 armed forces veterans were taking part, including 20 who served in the Second World War, 80 years on from the conflict's end.
Thousands of people lined Whitehall to pay tribute.
Sir Keir Starmer said: "This Remembrance Sunday, we pause as a nation to honour all those who have served our country. We reflect on the extraordinary courage of our armed forces in the world wars and subsequent conflicts, whose service secured the freedoms we cherish today."
The prime minister added: "Eighty years since the end of the Second World War, we remember a generation who stood against tyranny and shaped our future. Their legacy is peace and our duty is to protect it. Such sacrifice deserves more than silence, which is why this government remains committed to supporting veterans, their families and those who serve. Today, we remember, and we renew our promise to uphold the values they fought for."
Air Chief Marshal Sir Richard Knighton, chief of the defence staff, said: "From the Cenotaph in London to memorials in towns and villages across the United Kingdom, and wherever our armed forces serve around the world, we pause to remember their courage, their sacrifice and their enduring legacy. We shall remember them."
On Saturday night the King and Queen and the Princess of Wales were joined by Prince George at the Festival of Remembrance at the Royal Albert Hall.
Wearing a black suit, poppy pin and striped tie, the 12-year-old, who is second in line to the throne, sat next to his mother in the royal box.
Making his first attendance at the event, he watched intently as emotional videos of veterans speaking about their experiences and paying tribute to their lost friends and comrades played.
The crowd stood as the royal family entered to a fanfare of trumpets.
This year's festival, commemorating the 80th anniversary of the end of the Second World War, was hosted by the Ted Lasso actress Hannah Waddingham, who sang a rendition of Vera Lynn's We'll Meet Again. Waddingham spoke of the courage of her grandad, a war veteran "who at 109 still shares with me memories of his time in the Royal Navy".
The event also marked the 25th anniversary of the government lifting the ban on gay, lesbian and bisexual personnel serving openly in the armed forces. Starmer and his wife, Lady Victoria, arrived shortly before the royal family.
Performers included Sir Rod Stewart, Sam Ryder and Keala Settle, as well as the Central Band of the RAF, the RAF Squadronaires and the Band of HM Royal Marines.
The royal family stood and applauded as the Chelsea Pensioners entered the auditorium and marched across the stage while an orchestra gave a rendition of The Boys of the Old Brigade.
Veterans at the event included those who had helped to plan D-Day, some of whom had been prisoners of war or survived direct hits at sea.
George has made several public appearances this year as he is slowly eased into royal life. He also attended the VE Day 80 military procession in May with his parents and younger siblings, meeting Second World War veterans at Buckingham Palace.
The Duke and Duchess of Edinburgh were also at Saturday's event, sitting behind the King and Queen.
Kate's Alessandra Rich black dress was adorned with an HMS Glasgow brooch and a handmade poppy created out of silk, glass and other natural materials by Izzy Ager, of Lock and Co.
The Prince of Wales did not attend the event as he was returning from the Cop30 UN Climate Change summit in Belem, Brazil.
The Princess Royal is on an official visit to Australia and Singapore and attended a remembrance service and laid a wreath at the Anzac Memorial in Sydney.