The Queen and the Duke of Edinburgh are to visit Rome later this year for an audience with Pope Francis, Buckingham Palace has said.
The royal couple will also have a private lunch with Italian president Giorgio Napolitano.
The one-day trip in April was originally planned for last year but was postponed when the Queen fell ill.
The BBC's royal correspondent Peter Hunt said the Queen's "relaxed" meeting with the Pope will be at his residence.
He added that the Queen would not wear black or a veil, as she has done on three previous visits to the Vatican in deference to convention.
In 1980, the Queen dressed entirely in black, with a tiara holding a cascade veil in place, to meet Pope John Paul II in Rome, just as she had done on her visit to Pope John XXIII in 1961.
And in 2000, the Queen wore black again and a hat with a veil.
This was despite royal tradition that female members of the Royal Family do not wear black.
In a short statement, the palace said: "The Queen, accompanied by the Duke of Edinburgh, will visit Rome on Thursday 3 April.
"Her Majesty and His Royal Highness are visiting at the invitation of the president of Italy, President Napolitano.
"The Queen and the Duke of Edinburgh will visit the presidential palace where they will attend a private lunch hosted by the president.
"Following the private lunch Her Majesty and His Royal Highness will have an audience with His Holiness Pope Francis at the Vatican."
The 87-year-old Queen, who is head of the Church of the England, has been scaling back long-haul trips recently and is gradually handing over some of her responsibilities to her son and the future king, Prince Charles.
On Monday, the palace announced the Queen and Prince Philip were to make a three-day state visit to France in June.