The events of Bloody Sunday "can still shock and challenge us all", President Michael D Higgins has said.
Today marks the centenary of the day of violence in Dublin city during the War of Independence.
32 people were killed or fatally wounded in attacks, including 14 during a massacre in Croke Park during a football match between Dublin and Tipperary.
The President and the Taoiseach will lay a wreath at Croke Park this evening in memory of the victims, while 14 flames will be set alight on Hill 16 ahead of the Leinster football final between Dublin and Meath.
It's among the events being held around the capital and country to mark the 100th anniversary of an infamous day in Irish history.
In a statement, President Higgins said the past century has seen the events of 21st November 1920 "contested, obscured or selectively recalled for various purposes".
He said: "We recall today those lost and those who suffered with a sense of profound sadness and outrage even, but also as a reminder of the fragility of the hard-earned peace to which we have become accustomed and the consequences that flow from the abuse of power and the failure of diplomacy and politics.
"That the events that took place can, in their brutality and casualness to the taking of life, still shock and challenge us all is to be understood."
He said that different people on the island of Ireland may reflect on the events in different ways, and we must be respectful of that and open to differing perspectives.
Lord Mayor of Dublin Hazel Chu will also join in GAA commemorations, and will also lay a wreath at Dublin's Parnell Park.
Speaking ahead of the events, she said: "So many of us feel connected to the city we live in by reading stories of its past - but history is sown with bloody battles, massacres, and lost of lives.
"Sometimes the bloodshed and battles are on our very doorstep - so it's really important to remember that loss and those sacrifices."