Erasmus was a classical scholar who wrote in a "pure" Latin style and enjoyed the sobriquet "Prince of the Humanists." He has been called "the crowning glory of the Christian humanists." Using humanist techniques for working on texts, he prepared important new Latin and Greek editions of the New Testament. These raised questions that would be influential in the Protestant Reformation and Catholic Counter-Reformation. He also wrote The Praise of Folly, Handbook of a Christian Knight, On Civility in Children, Copia: Foundations of the Abundant Style, Julius Exclusus, and many other works.

Erasmus lived through the Reformation period and he consistently criticized some contemporary popular Christian beliefs. In relation to clerical abuses in the Church, Erasmus remained committed to reforming the Church from within. He also held to Catholic doctrines such as that of free will, which some Protestant Reformers rejected in favor of the doctrine of predestination. His middle road approach disappointed and even angered many Protestants, such as Martin Luther, as well as conservative Catholics. He died in Basel in 1536 and was buried in the formerly Catholic cathedral there, recently converted to a Reformed church.

Desiderius Erasmus was born in Rotterdam on October 28, 1466 . The exact year of his birth is debated but some evidence confirming 1466 can be found in Erasmus' own words. Of twenty-three statements Erasmus made about his age, all but one of the first fifteen indicate 1466. He was christened "Erasmus" after the saint of that name. Although associated closely with Rotterdam, he lived there for only four years, never to return. Information on his family and early life comes mainly from vague references in his writings. His parents almost certainly were not legally married. His father, named Roger Gerard, later became a priest and afterwards curate in Gouda. Little is known of his mother other than that her name was Margaret and she was the daughter of a physician. Although he was born out of wedlock, Erasmus was cared for by his parents until their early deaths from the plague in 1483. He was then given the very best education available to a young man of his day, in a series of monastic or semi-monastic schools, most notably a school run by the Brethren of the Common Life (inspired by Geert Groote) where he gleaned the importance of a personal relationship with God but eschewed the harsh rules and strict methods of the religious brothers and educators.

While at the Augustinian monastery Steyn near Gouda around 1487, young Erasmus wrote a series of passionate letters to a fellow monk, Servatius Rogerus, whom he called "half my soul", writing, "I have wooed you both unhappily and relentlessly". At any rate, this is hardly evidence for homosexual desire, but simply male-to-male friendship typical of the early modern period. Of similar interest, it has been assumed by some, was Erasmus' sudden dismissal by the guardian of Thomas Grey whom Erasmus tutored in Paris, which some have taken as grounds of an illicit affair . However, no personal denunciation was made of Erasmus during his lifetime, he took pains to condemn sodomy in his works, and instead praised sexual desire in the context of marriage between men and women.

In 1492, poverty forced Erasmus into the monastery. He was ordained to the Catholic priesthood and took vows as an Augustinian canon at Steyn at about the age of 25, but he never seemed to have actively worked as a priest for a longer time, and certain tenets of monasticism were among the chief objects of his attack in his lifelong assault upon Church excesses. Soon after his priestly ordination, he got his chance to leave the monastery when offered the post of secretary to the Bishop of Cambray, Henry of Bergen, on account of his great skill in Latin and his reputation as a man of letters. In order to allow him to accept that post, he was given a temporary dispensation from his monastic vows on the grounds of poor health and love of Humanistic studies, though he remained a "secular priest". Pope Leo X later made the dispensation permanent, a considerable privilege at the time.

In 1495, with the bishop's consent and stipend, he went on to study at the University of Paris, in the Collège de Montaigu, a centre of reforming zeal, under the direction of the ascetic Jan Standonck, of whose rigours Erasmus complained. The University was then the chief seat of Scholastic learning, but already coming under the influence of Renaissance humanism. For instance, Erasmus became an intimate friend of an Italian Humanist Publio Fausto Andrelini, poet and "professor of humanity" in Paris.

The chief centers of Erasmus's activity were Paris, Leuven (Louvain in Brabant), England, and Basel; yet he never belonged firmly in any one of these places. His time in England was fruitful in the making of lifelong friendships with the leaders of English thought in the stirring days of King Henry VIII: John Colet, Thomas More, John Fisher, Thomas Linacre and William Grocyn. At the University of Cambridge, he was the Lady Margaret's Professor of Divinity and had the option of spending the rest of his life as an English professor. He stayed at Queens' College, Cambridge, and may have been an alumnus.

In 1499, while in England, Erasmus was particularly impressed by the Bible teaching of John Colet who pursued a style more akin to the church fathers than the scholastics. This prompted him, upon his return from England, to master the Greek language, which would enable him to study theology on a more profound level and to prepare a new edition of Jerome's Bible translation. On one occasion he wrote Colet:

"I cannot tell you, dear Colet, how I hurry on, with all sails set, to holy literature. How I dislike everything that keeps me back, or retards me."

Despite a chronic shortage of money, he succeeded in learning Greek by an intensive, day-and-night study of three years, continuously begging his friends to send him books and money for teachers in his letters. Discovery in 1506 of Lorenzo Valla's New Testament Notes encouraged Erasmus to continue the study of the New Testament.