The Book of Luke is addressed to Theophilus.
The third of the Gospels is that of Luke. Luke was a companion of Saint Paul and he also wrote the Book of Acts. Both books are addressed to a man named Theophilus. We do not know who Theophilus was; the name means "lover of God" so it may be a title rather than a name. Theophilus may also have been a Roman official as he is referred to as "most excellent", a term used elsewhere to describe Roman officials.
Luke was a Greek from the city of Antioch in Syria, and he is the only Gentile author found in the New Testament. His Gospel is intended to strengthen the faith of Gentile Christians; especially Greeks. He also wants unbelieving Greeks to hear about Jesus and come to believe in Him.
Luke 15:25-32
"Now his elder son was in the field: and as he came and drew nigh to the house, he heard musick and dancing. And he called one of the servants, and asked what these things meant. And he said unto him, Thy brother is come; and thy father hath killed the fatted calf, because he hath received him safe and sound. And he was angry, and would not go in: therefore came his father out, and intreated him. And he answering said to his father, Lo, these many years do I serve thee, neither transgressed I at any time thy commandment: and yet thou never gavest me a kid, that I might make merry with my friends: but as soon as this thy son was come, which hath devoured thy living with harlots, thou hast killed for him the fatted calf. And he said unto him, Son, thou art ever with me, and all that I have is thine. It was meet that we should make merry, and be glad: for this thy brother was dead, and is alive again; and was lost, and is found"