Irish Taoiseach Enda Kenny said Margaret Thatcher was "a formidable leader" who "defined an era in British public life."
He said: "Mrs Thatcher was a formidable political leader who had a significant impact on British, European and world politics. During her 11 years as prime minister, she defined an era in British public life.
"While her period of office came at a challenging time for British-Irish relations, when the violent conflict in Northern Ireland was at its peak, Mrs Thatcher signed the Anglo-Irish Agreement which laid the foundation for improved North-South cooperation and ultimately the Good Friday Agreement.
"I extend my deepest sympathies to her family and the Prime Minister David Cameron."
More top news
A father has been found guilty of murdering his three-month-old son by hurling him "vigorously" against a hard surface in a fit of temper.
The self-styled revolutionary has spent the last 23 years in a high security prison for a string of murders and attacks.
Cancer surgeon accused of conducting series of 'completely unnecessary' operations denies giving cancer-phobic GP an unneeded mastectomy.