20 January – Ireland changed all road signage and regulations to use kilometres per hour (km/h). Distance and speed in Northern Ireland remained in miles per hour.
24 January – Former Minister for JusticeRay Burke was jailed for six months for tax evasion, as a result of legislation he introduced. He was the first Cabinet minister to be jailed as a result of tribunals of inquiry.
7 February – Taoiseach Bertie Ahern laid the foundation stone of a new town called Adamstown, just outside Lucan, County Dublin.
17 February – Seven people were detained by the Garda Síochána for suspected activities in relation to a bank heist in Belfast in December 2004. £2.3 million sterling was seized in County Cork.
11 March – The Irish Sugar Company factory in Carlow closed with the loss of several hundred jobs. It was Ireland's oldest sugar factory.
27 March – Cian O'Connor was stripped of his Olympic gold medal after the sports ruling body find that his horse, Waterford Crystal, had banned substances in its system during the Olympic Games in 2004.
8 April – President Mary McAleese and Taoiseach Bertie Ahern represented Ireland at the funeral of Pope John Paul II in Rome. A remembrance service was held at the papal cross in the Phoenix Park, Dublin.
16 April – The annual congress of the Gaelic Athletic Association voted to allow association football and rugby to be played in Croke Park under certain circumstances.
7 July – The Taoiseach met Pope Benedict XVI for a private audience in Rome.
16 July – Irish student, Tara Whelan (17), and a British holidaymaker were among five people killed in the Kuşadası minibus bombing in Turkey.
28 July – The Provisional Irish Republican Army made history by ending its armed campaign and ordering all its units to dump arms. The organisation also ordered its members not to engage in any other activities.
29 July – Forty-five-year-old Limerick woman, Dolores McNamara, won €115 million in the EuroMillions rollover jackpot prize. It was Europe's largest ever lottery jackpot.
7 September – Ireland lost 1–0 to France in a crucial football World Cup qualifying match.
15 September – Ireland reached its highest population since 1861. The increase consisted of the return of Irish people living abroad, and immigrants from Europe and Asia.
19 September – Irish Ferries offered voluntary redundancy packages to its 543 seafaring workers.
14 October – Roy Keane announced his retirement from international football following Ireland's failure to qualify for World Cup 2006 in Germany.
18 October – Tiede Herrema returned to the city of Limerick from which he was kidnapped 30 years ago in a high-profile case. Herrema presented his personal papers relating to the event to the University of Limerick Library.
20 October – The abducted journalist Rory Carroll was released unharmed after being kidnapped in Iraq the previous day.
1 November – The Government launched Transport 21, the biggest transport plan in the history of the state. It will allow €34.4 million to be spent on roads, rail, and the Dublin metropolitan area over a ten-year period.
