No, John the Baptist belongs to the New Testament.
I see John as part of both the New and Old Testaments.
John the Baptist is the “Elijah to come.” He is “to come” because he is part of the New Testament and “Elijah” because he is part of the Old Testament.
He must increase; I must decrease. (John 3:30)
John is the last of the great Old Testament prophets. He stands at the exact spot where Israel entered the promised land, at the Jordan River near the city of Jericho and baptizes Jesus. As the last great Old Testament prophet, he completes what Israel started, in the exact same place Israel started. Like the great prophets of the Old Testament, he is brutally murdered.
But John was sanctified by Jesus in the womb when his mother Elizabeth heard Mary’s greeting. After Mary, John was the first to be purified by Jesus, sanctified, consecrated to God’s service and sent on a mission. Even before Jesus was born, John is the first to be brought into Jesus’ Kingdom as a servant.
John is a bridge from the Old Testament to the New Testament, from the age of the prophets to the age of the fullness of God’s revelation of himself through the person of Jesus. John knows that the age of the prophets “must decrease” while the age of the fullness of truth “must increase” and John willingly accepts his mission as the final Old Testament prophet and arguably the first New Testament martyr (with all due respect to St. Stephen, of course).
If Mary is the first Christian, then John the Baptist is clearly the second.
And speaking of Mary…


I think the New Testament era starts with the words,
Hail, Full of Grace, the Lord is with you. (Luke 1:28)
The acorn of Christianity has fallen from the tree of Judiasm, and is about to grow.
-Tim-