Yet despite the vast popularity of the two popes, there is intense debate about whether these canonizations are nothing more than an elaborate public relations exercise — and whether they should be taking place at all.
John Paul II will hold the record for the fastest saint to be canonized in the history of the Catholic Church. John XXIII is even more controversial since Pope Francis approved his canonization with evidence of only one miracle — instead of the two normally required.
"It's controversial among the saint makers at the Vatican, who consider themselves sticklers when it comes to the miracle requirement," said longtime Vatican watcher John Thavis, author of "The Vatican Diaries."
"But Francis was actually using an ancient practice when he waived the second miracle requirement for John XXIII, recognizing that the faithful already know him to be a saint."
In fact, Francis — who has shown himself as a man not easily bound by tradition — is quickly making his mark on the sainthood process. Last year, he also waived the second miracle requirement for his favorite fellow Jesuit, Peter Favre, who died in 1546 and whose sainthood cause has languished since 1872.
It is not unprecedented to have a pope waive the second miracle requirement. The last one to do so was John XXIII himself, who in 1960 waived it for St. Gregorio Barbarigo, a 17th-century Venetian cardinal for whom John XXIII had a particular veneration.
When John Paul died in 2005, the streets of Rome were filled with shouts of "santo subito!" or "sainthood now!" His successor, Benedict XVI, waived the normal five-year waiting period so his sainthood could be fast-tracked.
Recognizing a miracle is a rigorous process. It is usually based on evidence of a cure that has no medical or scientific cause after an intense and lengthy investigation by a team of independent doctors, theologians and other consultants.
Monsignor Slawomir Oder, the Polish postulator responsible for spearheading John Paul's canonization, insisted Tuesday that the Vatican has strictly adhered to canon law and that John Paul is a worthy candidate.
"He was very reflective with a great capacity for prayer and meditation," Oder said. "John Paul II had that mystical depth of those who find God the source of life."
Born in Poland, Karol Wojtyla survived Nazi occupation of his homeland and as pope played a major role in the fall of communism. He is considered one of the most influential leaders of the 20th century.
Recognized around the world for his humanity and charisma, he survived an assassination attempt in 1981, traveled to 129 countries and touched the hearts of millions. He became the most traveled pope in history and proclaimed more saints than all his predecessors combined.
A tarnished legacy
Still, questions remain about whether John Paul did enough to respond to the clerical sex abuse scandal, in particular the activities of the founder of the Legion of Christ movement, Marcial Maciel Degollado.