Prime Minister David Cameron, First Minister Alex Salmond and the Prince of Wales were among those at Glasgow Cathedral today to honour the millions who died in the conflict.
The service featured poems, prayers and readings, reflecting the contribution of those from around the Commonwealth.
Charles's arrival was heralded by a fanfare by trumpeters from the Band of Her Majesty's Royal Marines Scotland.
Charles, who is known as the Duke of Rothesay in Scotland, was wearing the Royal Navy Ceremonial Day Dress with medals. He is Admiral of the Fleet of the Royal Navy.
Opening the service, Reverend Laurence Whitley, Minister of Glasgow Cathedral, said: "We meet because on a summer's day like this one, one hundred years ago, the world changed. Our nations and peoples found themselves in a war the like of which had never before been seen and the memory of which still haunts us all."
He added: "In this, the first of many services of commemoration and remembrance of the Great War to be held today and over the next four years, we have come to bow before God, to pray for peace and goodwill amongst the nations, to honour, to remember and to learn."
Others at the service included Deputy Prime Minister Nick Clegg, Labour leader Ed Miliband, Scottish Labour leader Johann Lamont, Scottish Conservative leader Ruth Davidson and Scottish Liberal Democrat leader Willie Rennie.
Sir Trevor McDonald set the scene to introduce many of the readings, such as a diary entry from Captain Ronald Rose of the 1st Cameronians, written on September 1, 1914, which was read by Captain Edward J Howell of 52nd Lowland, 6th Battalion The Royal Regiment of Scotland.
Capt Rose's death was described in a later diary entry on October 22, 1914, by one of his own men, Arthur Honeyball, which was read at the service by Private Dillon Rae, also of 52nd Lowland, 6th Battalion The Royal Regiment of Scotland.
Sir Trevor reminded the congregation that by the end of the war 6,146,000 men from across the British Isles had seen service, with 761,000 killed and 1,600,000 wounded, as well as 206,000 Irishmen of whom 30,000 died.
He also paid tribute to the those from around the Commonwealth who fought in the conflict.
He said: "During the years to come we shall rightly hear more of the courage and suffering of our forces in the conflict, but especially as this city has known the privilege of welcoming our Commonwealth brothers and sisters to the Games just past, it is right to pause now to remember their contribution."
Veteran BBC broadcaster Kate Adie also gave a reading, highlighting the role of women in the conflict, while Joanne Thomson, a 2014 graduate of the Royal Conservatoire Scotland, read a passage by the widow of poet Edward Thomas about their last night together before he was killed in the war.
The Prime Minister read a passage on service from St Mark's Gospel.
Others to give readings included Sir Peter Cosgrove, Governor-General of Australia, Mr Gordon Campbell, High Commissioner for Canada, and Lieutenant General Sir Jerry Mateparae, Governor-General of New Zealand.
The final reading came from Kirsten Fell, 16, a pupil at Dunbar Grammar School, reflecting on a school trip she went on to Flanders in 2013.
Everyone attending the event at the cathedral found a poppy placed on their seat, which Reverend Whitley asked them to take away and place wherever they feel appropriate.
As the service ended, a procession of children walked down the aisle carrying candles to symbolise the "candle of peace and hope" passing to the new generation.
Following the memorial, the Duke and Mr Cameron attended a reception at the City Chambers on George Square.
They were introduced to the family of Henry May, from Bridgeton, Glasgow, who was awarded the Victoria Cross for saving the life of a comrade in France in October 1914.
They viewed a display by Glasgow University which is carrying out research into the story of the university community during the war.
Council building apprentices showed Charles and Mr Cameron the commemorative benches they have been producing which will be placed around the city.
Charles himself has a link with the conflict as his own great uncle Captain Fergus Bowes-Lyon was killed in the Battle of Loos which preceded the Somme campaign.
His wife Camilla's family suffered the loss of three brothers, who would have been her great uncles, in the 1914-18 war including one - Henry Cubbitt - who died at the Somme in 1916.
The Duke of Rothesay laid a wreath followed by Mr Cameron and Glasgow Lord Provost Sadie Docherty.
Mr Clegg and Mr Miliband then also laid wreaths.
Hundreds of people gathered at George Square for the wreath-laying ceremony, also led by Reverend Whitley.
Chief Secretary to the Treasury Danny Alexander, Home Secretary Theresa May and Eric Pickles, Secretary of State for Communities, were among those who attended the hour-long service in the heart of the city.
Charles, sitting next to Mr Cameron, listened as prayers were said and a bugler played the Last Post.
Members of the public lined the square to pay their respects, many of them clutching union flags.
Beverley Paul from Cumbernauld outside Glasgow took her three children aged 11, 14 and 18 to watch the ceremony.
She said: "I just wanted to support the troops and the people who gave their lives for us, and also educate my children.
"I've got friends and family in the Armed Forces and we should remember the fallen."
The Duke and Mr Cameron earlier met Jennifer McInnes, 42, whose great grandfather Henry May served as a Private with the Cameronians and carried out the courageous rescue of Lieutenant Douglas Alexander Graham at La Boutillerie, dragging him 300 yards to safety while under heavy fire.
Ms McInnes said: "It's a pleasure to be part of the commemorations in Glasgow. We are only here because of the brave actions of people like my great grandfather that day.
"When he received the Victoria Cross he said 'I only did what any other soldier would have done'."
She added: "I think it means a lot that important people are marking the centenary here in Glasgow."
City Building apprentice Graeme Howe, 22, was keen to get involved in the council's commemorative bench project as his great grandfather Thomas Howe fought in the war with the 1st Battalion, Highland Light Infantry.
He said: "I was glad to be part of the project and it was great to meet the Prince - he seemed really interested."
Dr Tony Pollard, director of the Great War project at Glasgow University, said: "Over 4,500 people from the university community served during the war - men and women - and 760 were killed.
"What we're trying to do is tell the story of that experience. It wasn't just fighting on the western front, it was a global war.
"There's a lot of enthusiasm for the project."