according to Christian tradition, a king of Arabia and youngest of the three Magi who visited Jesus and gave the gift of myrrh; usually portrayed in paintings with the darkest hair of the three kings, or the darkest skin of the three kings
Balthazar is a traditional name for one of the Magi who visited Jesus; the Gospel of Matthew neither names the Magi nor says there were exactly three.
Biography
Matthew 2 describes Magi from the east who came to Jerusalem seeking the newborn king of the Jews, followed the star to Jesus, worshiped Him, and presented gold, frankincense, and myrrh. The later names Balthazar, Caspar, and Melchior developed in Christian tradition, as did many details about their number, ages, and kingdoms. Those details are not supplied by Matthew.
Biblical Significance
For a biblical-figures database, Balthazar should be marked as a later traditional identification rather than a named New Testament person. The biblical subject is the unnamed Magi collectively.