Pope Francis canonized Pope John the XXIII and Pope John Paul II, two 20th-century pontiffs who changed the course of the Catholic Church.
Sunday's historic ceremony drew hundreds of thousands of people to Vatican City.
"They were priests, bishops and popes of the 20th century," Francis told the crowd. "They lived through the tragic events of that century, but they were not overwhelmed by them."
"John XXIII and John Paul II cooperated with the Holy Spirit in renewing and updating the church in keeping with her pristine features, those features which the saints have given her throughout the centuries," Francis said.
Vatican observers believe that Pope Francis approved the two popes for simultaneous sainthood to signal that Catholics of different views are welcome in the church.
Pope John the XXIII, who served from 1958 to 1963, is known for his modernizing reforms.
Conversely, Pope John Paul II, who served from 1978 to 2005, is known for upholding orthodoxy and doctrine and putting some controls around the earlier pope's reforms.
From the moment he took office, Pope John Paul stood as a symbol of faith and freedom for his homeland of Poland, caught in the grip of communism.
Shortly after becoming pope, he returned there, where his anti-communist stance endeared him to the solidarity movement.
John Paul II always said he was not Superman who let communism fall.
"The tree was rotten. I just shook the tree," he said.
Many also remember John Paul as the first truly global pope. He visited more than 120 countries -- the most ever for a pope -- and held audiences with more than 17 million people.
But there remains a stain on his legacy: the sex abuse scandal that festered for years on his watch.
"Certainly he was against sex abuse. He was tough against sex abuse, but he should have opened an investigation about the founder of the Legionaries of Christ, Marcial Maciel," said Marco Politi, Vatican analyst and Vatican correspondent for the Italian newspaper Il Fatto Quotidiano.
Despite this, many now call John Paul "the great" in honor of his efforts to fight communism and inspire a new generation of Catholics.
And in Poland this week, the government is supporting an exhibit entitled, "Pope of Freedom -- in Recognition of His Rise to Sainthood."