Luke 21 is the twenty-first chapter of the Gospel of Luke in the New Testament of the Christian Bible. It records the observations and predictions of Jesus Christ delivered in the temple in Jerusalem, and his exhortation "to be watchful". The book containing this chapter is anonymous, but early Christian tradition uniformly affirmed that Luke the Evangelist composed this Gospel as well as the Acts of the Apostles.

The Olivet Discourse or Olivet prophecy is a biblical passage found in the Synoptic Gospels in Matthew 24 and 25, Mark 13, and Luke 21. It is also known as the Little Apocalypse because it includes the use of apocalyptic language, and it includes Jesus's warning to his followers that they will suffer tribulation and persecution before the ultimate triumph of the Kingdom of God. The Olivet discourse is the last of the Five Discourses of Matthew and occurs just before the narrative of Jesus's passion beginning with the anointing of Jesus.