Pope Francis made two Portuguese shepherd children who reported seeing visions of the Virgin Mary the latest Catholic saints.
Francisco and Jacinta Marto are the youngest-ever saints who didn't die as martyrs.
Their visions turned the Portuguese farm town of Fatima into one of the world's most important Catholic shrines.
Francis canonised the siblings at the start of a Mass marking the centenary of their visions.
Half a million people watched in the vast square in front of the shrine's basilica, the Vatican said.
"It is amazing. It's like an answer to prayer, because I felt that always they would be canonised," said Agnes Walsh who had travelled from Killarney, Ireland. She said she prayed to Francisco Marto for 20 years, hoping her four daughters would meet "nice boys like Francisco."
Francisco and Jacinta, aged 9 and 7, and their 10-year-old cousin, Lucia, reported that the Virgin Mary made half a dozen appearances to them as they grazed their sheep. They said she confided in them three secrets foretelling apocalyptic visions of hell, war, communism and the death of a pope.
At the time, Europe was in the throes of World War I, and the Portuguese church was suffering under anti-clerical laws from the republican government that had forced many bishops and priests into exile.