The queen, Prince Charles, presidents and prime ministers rose to applaud veterans, their coats heavy with medals, as they stood on a giant stage beside a guard of honour after a film of the Normandy landings was shown.
"The wartime generation - my generation - is resilient, and I am delighted to be with you in Portsmouth today," the 93-year-old queen, wearing bright pink, said.
Prime Minister Theresa May was joined for the commemorative events in Portsmouth by US President Trump, who is on the final day of a state visit to Britain, and his wife, Melania.
Trump read a prayer given by Franklin D. Roosevelt in 1944 - "The enemy is strong. He may hurl back our forces but we shall return again and again; and we know that by Thy grace, and by the righteousness of our cause, our sons will triumph."
French President Emmanuel Macron, Canadian Prime Minister Justin Trudeau, Australian Prime Minister Scott Morrison, German Chancellor Merkel, and leaders and senior figures from 10 other countries also attended.
On Wednesday some 300 veterans took part on D-Day, all now older than 90. They left Portsmouth on a specially commissioned ship, MV Boudicca, and retraced their 1944 journey across the English Channel, accompanied by Royal Navy vessels and a lone wartime Spitfire fighter plane.