Pope Francis is to visit the United States next year.
He plans to travel to Philadelphia in September for the World Meeting of Families, a conference held every three years in a different city to celebrate the importance of family.
Pope Francis' announcement, at an interreligious Vatican conference on traditional family values, ended months of lobbying and speculation.
Philadelphia mayor Michael Nutter, Pennsylvania governor Tom Corbett and conference organiser Philadelphia Archbishop Charles Chaput met the pope at the Vatican and invited him to the city in March. Vatican officials toured the city in May.
Just last week, more than 10,000 Philadelphia Catholic school children sent handwritten notes encouraging Pope Francis to make the visit.
Archbishop Chaput was at the Vatican for Pope Francis' announcement today and said: "I applauded the loudest."
Pope Francis, making just the second papal visit to Philadelphia and his first visit to the US as pope, is expected to participate in the conference's closing events and celebrate a Mass on the Benjamin Franklin Parkway.
The boulevard, linking Philadelphia's city hall to the art museum steps made famous by the movie Rocky, is home to the Cathedral Basilica of Saints Peter and Paul and has been the backdrop for summer concerts and parades attracting hundreds of thousands of people.
Officials have said the World Meeting of Families on September 25-27 next year could attract more than a million people. Hotels within a 10-mile radius of centre city Philadelphia have already sold out.
Pope Francis is also expected to address Congress and deliver a speech to the United Nations in New York to mark its 70th anniversary.
Details of the pope's itinerary will not be finalised until next spring or summer, conference organisers said.
Pope John Paul II, canonised by Pope Francis in April, celebrated Mass on the Benjamin Franklin Parkway in front of an estimated one million people in 1979.
Pope Francis' predecessor, Pope Benedict, was the last pontiff to visit the US. He celebrated Mass in New York and Washington, met President George W Bush and spoke to the United Nations during a five-day trip in April 2008.