The currency in the Republic of Ireland is the Euro, €. However, in Northern Ireland it is Pound Sterling £.
What is the current exchange rate? (this is updated regularly but you can check with your bank before you leave should you wish)
1 Euro = 0.80 pounds sterling (approximately at time of typing)
1 Euro = 1.10 United States Dollar (approximately at time of typing)
1 Euro = 1.50 Canadian Dollar (approximately at time of typing)