Final answer:
The Saint's day in 1572 on which Catherine de Medici had 3,000 Protestants killed in Paris is known as St. Bartholomew's Day. This tragic event is known as the St. Bartholomew's Day Massacre.
Step-by-step explanation:
The mass murder of Protestants in Paris in 1572 occurred on the day of St. Bartholomew. This event is infamously known as the St. Bartholomew's Day Massacre. Catherine de Medici, who was the queen mother, is generally considered responsible for this brutal act. It is estimated that approximately 3,000 Protestants were killed during this massacre in Paris, however, the brutality of this event extended beyond the borders of Paris into other parts of France.
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