Pope Francis has beatified his predecessor at a ceremony in St. Peter's Square before tens of thousands of people. Beatification is the last step before sainthood in the Roman Catholic Church.
John Paul was known as "The Smiling Pope" because of his meekness and simplicity.
"With a smile, Pope John Paul managed to communicate the goodness of the Lord," Francis said in his homily, speaking as people huddled under umbrellas in a thunderstorm.
"How beautiful is a Church with a happy, serene, and smiling face, that never closes doors, never hardens hearts, never complains or harbours resentment, does not grow angry or impatient, does not look dour or suffer nostalgia for the past".
Born Albino Luciani into poverty in a northern Italian mountain village in 1912, he was ordained a priest in 1935, a bishop in 1958 and a cardinal in 1973.
He was elected pope on Aug. 26, 1978 following the death of Pope Paul VI, taking the name John Paul to honour his two immediate predecessors. He was found dead in bed by two nuns on Sept. 29.
Doctors said he died of a heart attack and aides said he had complained of chest pains the day before but did not take them seriously.
At first, the Vatican, uneasy saying two women had entered the pope's bed chambers, said he was found lifeless by a priest. The Vatican corrected itself but the misstep sprouted conspiracy theories.
In 1984 "In God's Name - An Investigation into the Murder of Pope John Paul I," by British author David Yallop that argued the pope was poisoned by a cabal linked to a secret Masonic lodge, spent 15 weeks in the New York Times bestseller list.
The New York Times own review of the book, however, ridiculed Yallop's investigative techniques and in 1987 another Briton, John Cornwell, wrote a book called "A Thief in the Night," meticulously dismantling conspiracy theories.
Although widely debunked, the idea of a pope being murdered in his bedroom in the 20th century irresistibly entered the collective consciousness, and in the film "The Godfather Part III, a pope named John Paul I was killed with poisoned tea.
Italian journalist and author Stefania Falasca, who spent 10 years documenting John Paul's life and viewed his medical history, wrote several books about him. She called the conspiracy theories "publicity-driven garbage".
John Paul is attributed with the miracle healing of an 11-year-old Argentine girl who had a severe brain inflammation, epilepsy, and suffered septic shock. Her parents prayed to him.
The Roman Catholic Church teaches that only God performs miracles, but that saints, who are believed to be with God in heaven, intercede on behalf of people who pray to them.
Another miracle will be necessary for John Paul to be declared a saint.