Who was the first Roman Catholic monarch?

Answer 1

Constantine, although he was technically emperor and not king.

Catholicism began in various cities in the ancient world when the teachings of the apostles and their students began to spread. Each city that Christianity (early Catholicism) took root in modified interpretations of scripture according to previous local customs. The leader of the Christians in each city became known as a Bishop. Roman Catholicism can't be said to have even begun until the Christian community of the city of Rome came together under the head of a Bishop. While the Bishop of Rome was always an important figure, it was several years before the Bishop of Rome was claimed to be THE senior bishop, holding dominion over the others. Several bishops in other countries and cities refused to acknowledge the supremacy of the Roman Bishop, mostly because Rome at the time was still mostly under the control of the Imperial Cult and the various Roman Cults devoted to different deities. The bishops that refused to bow to the Pope became heads of their own Catholic churches, most of which operate more or less independently of the Vatican to this day.

The first Ruler of the Roman Empire to declare himself Christian, and thus under the spiritual guidance (authority) of the Roman Bishop, was the Emperor Constantine, who also issued the first edict (the Edict of Milan, year 313) that called for religious tolerance of the christian cult. So, technically, Emperor Constantine was the first Roman Catholic monarch of all time.

Answer 2

Constantine, although he was technically emperor and not king.

Catholicism began in various cities in the ancient world when the teachings of the apostles and their students began to spread. Each city that Christianity (early Catholicism) took root in modified interpretations of scripture according to previous local customs. The leader of the Christians in each city became known as a Bishop. Roman Catholicism can't be said to have even begun until the Christian community of the city of Rome came together under the head of a Bishop. While the Bishop of Rome was always an important figure, it was several years before the Bishop of Rome was claimed to be THE senior bishop, holding dominion over the others. Several bishops in other countries and cities refused to acknowledge the supremacy of the Roman Bishop, mostly because Rome at the time was still mostly under the control of the Imperial Cult and the various Roman Cults devoted to different deities. The bishops that refused to bow to the Pope became heads of their own Catholic churches, most of which operate more or less independently of the Vatican to this day.

The first Ruler of the Roman Empire to declare himself Christian, and thus under the spiritual guidance (authority) of the Roman Bishop, was the Emperor Constantine, who also issued the first edict (the Edict of Milan, year 313) that called for religious tolerance of the christian cult. So, technically, Emperor Constantine was the first Roman Catholic monarch of all time.