At a final Mass, the pope encouraged a shake-up in the Catholic church.
Millions cheered the Latin American pope as he made his way back to the beach for Sunday's Mass. This was the third time he spoke to the youths gathered for World Youth Day celebrations on the beach, having addressed them the night before during an all-night vigil and earlier in the week.
"Go and make disciples of all nations," Pope Francis told the crowd on Sunday, noting that "faith is a flame that grows stronger the more it is shared and passed on."
"The church needs you, your enthusiasm, your creativity and the joy that is so characteristic of you," he said to cheers.
The whole 2.5-mile (four-kilometer) crescent of Copacabana's broad beach was teeming with people on Sunday, many having spent the night. Throughout their all-night vigil, the Catholic youths danced, prayed and sang.
The pope thrilled the crowds Sunday morning, stopping to catch gifts, kiss babies and generally work the crowd. For many, the experience was something they will never forget.
"We were dying of cold, but it was worth it," said Lucrecia Grillera, an 18-year-old Argentine who was in the crowed. "It was a tiring day, but it was a great experience."
The Vatican said more than 3 million people gathered for Sunday's Mass, basing the number on information from World Youth Day organizers and local authorities. The turnout was much bigger than the one million who turned out for the last World Youth Day in Madrid in 2011.
In addition to the millions of young people, world leaders also attended the Mass. Brazilian President Dilma Rousseff, Argentine President Cristina Fernandez, Bolivian President Evo Morales, as well as leaders from Suriname, Uruguay and Panama were on hand.
The pope finished his sermon with a call for evangelization.
"Jesus Christ is counting on you! The Church is counting on you! The pope is counting on you!" he said.
Later on Sunday the pope was expected to meet with Latin American and Caribbean bishops before leaving for Rome in the evening.
tm/dr (dpa, AP, Reuters)