9 January – The Lillebonne, the largest vessel ever constructed in Dublin, was successfully launched in the North Wall Yard.
16 February – Explosions caused by petrol fumes after refuelling on board the newly commissioned submarine HMS A5 killed six of the eleven crew at the Royal Navy's base in Haulbowline.
6 March – The obligation of the Post Office towards letters addressed in Irish was raised in the British House of Commons. The debate arose because the General Post Office in Dublin returned parcels addressed in Irish by the Gaelic League.
29 May – Statistics in 1904 showed that nearly 37,000 people emigrated. Since 1851, almost four million people have left the island.
^"Church House and Assembly Buildings". About the Presbyterian Church. Presbyterian Church in Ireland. Archived from the original on 28 November 2012. Retrieved 27 July 2012.
^ abcHayes, Dean (2006). Northern Ireland: International Football Facts. Belfast: Appletree Press. p. 158. ISBN 0-86281-874-5.