Charles, who served himself in the Royal Navy and Royal Air Force, told the flag-waving audience to "give thanks for all those who gave so much to win the victory whose fruits we still enjoy to this day".
"Let us once again commit ourselves always to remember, cherish and honour those who served that day," he said.
The date pays tribute to the soldiers who fought to liberate France, in a major turning point of World War II.
4,400 Allied troops died on D-Day.
Wednesday's UK commemorations, which included readings, music and re-enactments from the period, also heard from aging veterans.
Roy Hayward—who was aged 19 at the time— lost both his legs below the knees to amputation during the war.
"I always considered myself one of the lucky ones that survived, because so many of us didn't," Mr Hayward said.
"I represent the men and women who put their lives on hold to go and fight for democracy and this country.
Veterans also gathered in Ouistreham, France to pay tribute.
Aged between 97 and 103, many of the veterans had walking sticks or were in wheelchairs, and wore military medals pinned to their lapels.
John Dennett, 99, told the BBC he was looking forward to the ceremonies of the coming days.
"It's a chance of a lifetime," he said.
AFP/
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