Christianity in the 1st century covers the formative history of Christianity from the start of the ministry of Jesus to the death of the last of the Twelve Apostles and is thus also known as the Apostolic Age. Early Christianity developed out of the eschatological ministry of Jesus. Subsequent to Jesus' death, his earliest followers formed an apocalyptic messianic Jewish sect during the late Second Temple period of the 1st century. Initially believing that Jesus' resurrection was the start of the end time, their beliefs soon changed in the expected Second Coming of Jesus and the start of God's Kingdom at a later point in time.

Gospel originally meant the Christian message, but in the 2nd century it came to be used also for the books in which the message was reported. In this sense a gospel can be defined as a loose-knit, episodic narrative of the words and deeds of Jesus, culminating in his trial and death and concluding with various reports of his post-resurrection appearances. Modern biblical scholars are cautious of relying on the gospels uncritically, but nevertheless, they provide a good idea of the public career of Jesus, and critical study can attempt to distinguish the original ideas of Jesus from those of the later Christian authors.