The Queen and Northern Ireland's Deputy first minister Martin McGuinness have shaken hands.
Their meeting comes 14 years after peace was declared in the North of Ireland.
The historic handshake draws a line under a conflict that cost the lives of thousands of soldiers and civilians, including that of the Queen’s cousin.
Lord Louis Mountbatten was killed by the IRA in 1979 with three others, including his 14-year-old grandson, when his boat was blown up while he was on holiday in Ireland.
The Queen also met Northern Ireland's Unionist first minister Peter Robinson and Irish President Michael D.Higgins at the meeting behind closed doors in a theatre in a leafy suburb of Belfast that was cordoned off by hundreds of police.
Mr McGuinness shook the hand of the Queen for the second time as she left the theatre, this time in front of television cameras.
Mr McGuinness wished the smiling monarch well in Irish, saying "Slán agus beannacht", which he told her means "Goodbye and god speed".
The vast majority of the North’s politicians backed the meeting.
"Today is a huge event and it is, in a sense, the ultimate handshake," John Reid, British Secretary of State for Northern Ireland from 2001 to 2002, told the BBC.
"On all sorts of levels this is a hugely significant step but it is only one more step in a long process. This may take generations - to get back to absolute reconciliation in Northern Ireland and the island of Ireland."
Mr McGuinness said of the meeting: "It is physically impossible for me to stretch out the hand of friendship, peace and reconciliation to hundreds of thousands of unionists.
"I have shaken the hands of many unionists over the course of recent years, people who have appreciated my contribution and my party's contribution to peace. But in shaking the hand of Queen Elizabeth I am effectively, symbolically, shaking the hands of hundreds of thousands of unionists.
"I think that is a good thing. I think that is something that is very important to do, particularly in showing unionists that a spirit of generosity on all sides can pay huge dividends for all of us."
