The Nativity of St. John the Baptist (or Birth of John the Baptist, or Nativity of the Forerunner) is a Christian feast day celebrating the birth of John the Baptist, a prophet who foretold the coming of the Messiah in the person of Jesus and who baptized Jesus.

Christians have long interpreted the life of John the Baptist as a preparation for the coming of Jesus Christ, and the circumstances of his birth, as recorded in the New Testament, are miraculous. The sole biblical account of birth of John the Baptist comes from the Gospel of Luke. John’s parents, Zechariah or Zachary — a Jewish priest — and Elizabeth, were without children and both were beyond the age of child-bearing. During Zechariah's rotation to serve in the Temple in Jerusalem, he was chosen by lot to offer incense at the Golden Altar in the Holy Place. The Archangel Gabriel appeared to him and announced that he and his wife would give birth to a child, and that they should name him John. However, because Zechariah did not believe the message of Gabriel, he was rendered speechless until the time of John's birth; at that time, his relatives wanted to name the child after his father, and Zechariah wrote, "His name is John" and could speak (Luke 1:5-25; 1:57-66). Following Zechariah's obedience to the command of God, he was given the gift of prophecy, and foretold the future ministry of John (Luke 1:67-79).