By Zamira Rahim
In Paris, at the biggest of the events marking the occasion, over 100 world leaders and dignitaries walked towards the Arc de Triomphe to stand before the grave of the unknown soldier.
French president Emmanuel Macron made a speech warning against the dangers of nationalism, in what was interpreted as a veiled criticism of US President Donald Trump, who was among the gathered dignitaries.
Angela Merkel, Vladimir Putin and Justin Trudeau were also present.
"Patriotism is the exact opposite of nationalism," Mr Macron said.
"Nationalism is a betrayal of patriotism. In saying 'Our interests first, whatever happens to the others,' you erase the most precious thing a nation can have, that which makes it live, that which causes it to be great and that which is most important: Its moral values."
By Angelique Chrisafis in Paris
“Old demons are resurfacing. History sometimes threatens to take its tragic course again and compromise our hope of peace. Let us vow to prioritise peace over everything.”
He said the traces of the first world war had never been erased from Europe nor the Middle East and called on countries to stand together in “goodwill” against climate change, poverty and inequality. “Let us build our hopes rather than playing our fears against each other.”