Final answer:
The Society of Jesus, or Jesuits, was the most significant religious order during the Catholic Reformation, known for its educational, advisory, and missionary roles, including efforts to convert natives in places like Canada.
Step-by-step explanation:
The most important religious order that arose during the Catholic Reformation and played a significant role in education, missionary work, and the combat against the spread of Protestantism was the Society of Jesus, or the Jesuits. Founded by Ignatius of Loyola in the 1540s, its members established many schools, seminaries, and engaged in missionary efforts across the world, including in newly discovered territories.
The Jesuits were influential in both the conversion of non-Christians to Roman Catholicism and providing counsel to Catholic rulers in Europe, without having a female branch associated with their order. Their activities extended to places like Canada where they endeavored to convert native populations to Catholicism, and their detailed annual reports, known as the Jesuit Relations, provide rich historical insights into that era.