The street and square are named after Oliver FitzWilliam, 1st Earl of Tyrconnell who lived at Merrion Castle.

[2] The garden entrance of Leinster House, formerly Kildare House, the seat of a major aristocratic house, is located on the street as is Irish Government Buildings, formerly the Royal College of Science for Ireland, and the main location of the Department of the Taoiseach and other arms of government.

Some reports suggest that Field Marshal The 1st Duke of Wellington was born in his family’s Mornington House on the street.

[3] Between 1904 and 1922, all the houses on one side of the street were demolished and replaced by the Royal College of Science for Ireland, which became Government Buildings and was designed by Sir Aston Webb.

[3] A joint press meeting was held between Enda Kenny and British Prime Minister Theresa May in Merrion Street on 30 January 2017, to discuss the implications of Brexit on Northern Ireland and Ireland.