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
The Hollywood actor and environmental campaigner met the president-elect to discuss the economic advantage of green policies.
The Pirates of the Caribbean star brought in just $2.80 (£2.21) at the box office for every dollar he was paid for his last three films.
Junk food advertising is to be banned across all children's media - including online and social - in a bid to tackle childhood obesity.