About 10,000 police and security personnel and special paramedic teams were deployed and large areas of Rome were closed to traffic.
Pilgrims who did not want to battle the crowd spent the night praying in Rome churches left open especially for the event and would watch the event on large television screens around the city.
The election of the Argentinian-born Pope Francis has injected fresh enthusiasm into a Church beset by sexual and financial scandals during the papacy of his predecessor Benedict XVI, who last year became the first pope to resign in 600 years.
He now lives in secluded retirement but will be present at the canonization mass, which will symbolically bring together four popes. The two new saints are buried in crypts in St. Peter's Basilica.
The fact that the two being canonized are widely seen as representing contrasting faces of the Church has added to the significance of an event that
Francis hopes will draw the world's 1.2 billion Catholics closer together.
John, an Italian often known as the "Good Pope" because of his friendly, open personality, died before the Second Vatican Council ended its work in 1965 but his initiative set off one of the greatest upheavals in Church teaching in modern times.
The Council ended the use of Latin at Mass, brought in the use of modern music and opened the way for challenges to Vatican authority, which alienated some traditionalists.
John Paul was widely credited with helping to bring down communist rule in eastern Europe and hastening the end of the Cold War. He continued many of the reforms but tightened central control, condemned theological renegades and preached a stricter line on social issues such as sexual freedom.
A charismatic, dominant pope, he was criticised by some as a rigid conservative but the adoration he inspired was shown by the huge crowds whose chants of "santo subito!" (make him a saint at once!) at his funeral 2005 were answered with the fastest declaration of sainthood in modern history.
Both canonisations have involved some adaptation of the normally strict rules governing declaration of a saint, which involve a close examination of each candidate's life and works and normally the attestation of at least two miracles.
Benedict waived a rule that normally requires a five-year waiting period before the preliminaries to sainthood can even begin to speed up John Paul's canonisation, while Francis ruled that only one miracle was needed to declare John a saint.