Thinking the Jesuit missions of the 17th century means studying the world of Antônio Vieira’s Fifth Empire Prophecies, but it also means studying the concrete missionary experience of this “universal man”. In fact, he projected his imagination of entirely new political realities into the future. In 1653, Antônio Vieira, who was the superior of the Jesuit Mission, arrived in Maranhão with great hopes of spreading the Gospel among the natives of the basin of the Amazon river. In this huge territory, he had a dream: “The Fifth World Empire” (O Quinto Império do Mundo). The objectives of this Empire are prophesized in his letters, sermons, books and manuscripts written while he was travelling on the rivers that cross the tropical forest. This article suggests that Vieira’s missionary experience gave birth to the dream of the Fifth Empire which is explained in his book História do Futuro and in a text never concluded, the Clavis Prophetarum.