Around a quarter of a million people went to the commemorations in Dublin, a century after militia stormed the city's General Post Office and declared Ireland independent to Britain.
Almost 500 people were killed in the Easter Rising, more than half of which were civilians.
The British Army stopped the rebellion in less than a week and executed 15 of the main people involved in it.
The British response to the uprising, which also included sending thousands of people to prisons and what would now be considered concentration camps, led to greater support for Irish independence.
Ireland's President Michael D Higgins (below) laid a wreath at the spot where the 15 rebels were executed.
Prayers were said before acting Taoiseach Enda Kenny invited the head of State to lay the wreath "on behalf of the people of Ireland in honour of all those who died".
After a minute's silence, a lone piper from the Army No 1 Band played the lament Wrap The Green Flag Around Me Boys, before the Last Post was sounded.
The Irish Tricolour, which flew at half mast throughout, was then raised.
Head Chaplain to the forces, Fr Séamus Madigan, said: "On this Easter Day of new beginnings, we remember the men, the women and the children of 1916 whose short lives and big dreams extended the horizons of our hopes.
"Look kindly [God], we pray, on all who lost their lives in 1916 and throughout the troubled history of our island."
