The first minister has congratulated the Duke and Duchess of Cambridge on the birth of their son.
Peter Robinson said he wanted to extend his best wishes to them on behalf of everyone in Northern Ireland.
"I was honoured to attend their wedding and I wish them every health and happiness in the next chapter of their lives together," he said.
The Duchess of Cambridge gave birth to a boy weighing 8lb 6oz at 16:24 BST on Monday at St Mary's Hospital in London.
Secretary of State for Northern Ireland Theresa Villiers sent her congratulations.
"People across Northern Ireland will welcome this wonderful news. I send warmest wishes to the Royal couple on the birth of the prince," she said.
On Monday night, Deputy First Minister Martin McGuinness said there had been some interest in his thoughts on the Royal baby.
"I extend warmest best wishes to all parents and new babies born today.
"God bless them."
Ulster Unionist leader Mike Nesbitt MLA said it was: "Brilliant news for William and Kate, and all the Royal family.
"First and foremost, it is great to hear that mother and child are both well, and we wish the new parents all the very best," he said.
"The United Kingdom can now enjoy the next few days as we celebrate the birth of the latest addition to the Royal family."
The Grand Orange Lodge of Ireland also offered its best wishes to the Duke and Duchess of Cambridge.
Grand Master Edward Stevenson said: "Today's announcement will be met with great joy particularly here in Northern Ireland, where the Royal family is held in such high esteem and unrivalled affection.
"Members of the Orange fraternity around the globe, including the Republic of Ireland, will also be heartened by this magnificent news."
Alliance East Belfast MP Naomi Long said: "I would like to offer my congratulations to the Duke and Duchess of Cambridge following the birth of their son.
"I hope that they will be afforded some privacy in their first few days and weeks of parenthood."
President of the Methodist Church in Ireland, The Rev. Dr. Heather Morris, said: "In common with a multitude of people I rejoice at the safe delivery of the new royal prince.
"I pray that he along with his parents, will experience the blessing of God today and for the rest of their lives."
TUV Leader Jim Allister said the birth of a prince was something special.
"It is, of course, a joyous occasion for the royal family but it is also something the entire nation feels part of.
"People across Northern Ireland will welcome this news and look forward to the day when the Prince becomes King of Great Britain and Northern Ireland."
Kensington palace said in a statement that the duchess and the baby were "doing well" and would stay in hospital overnight.
The news has been displayed on an ornate easel in the forecourt of Buckingham Palace in line with tradition.
A bulletin - signed by the Queen's gynaecologist Marcus Setchell, who led the medical team that delivered the baby - was taken by a royal aide from St Mary's to the palace under police escort.
The document said: "Her Royal Highness, the Duchess of Cambridge was safely delivered of a son at 4.24pm today.
"Her Royal Highness and her child are both doing well."
The press release said the Duke of Cambridge was present for the birth.
"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news," it said.