Johann Reuchlin was born at Pforzheim in the Black Forest in 1455, where his father was an official of the Dominican monastery. According to the fashion of the time, his name was graecized by his Italian friends into Capnion (Καπνίων), a nickname which Reuchlin used as a sort of transparent mask when he introduced himself as an interlocutor in the De Verbo Mirifico. He remained fond of his home town; he constantly calls himself Phorcensis, and in the De Verbo he ascribes to Pforzheim his inclination towards literature.
Here he began his Latin studies in the monastery school, and, though in 1470 he was for a short time at Freiburg, that university seems to have taught him little. Reuchlin's career as a scholar appears to have turned almost on an accident; his fine voice gained him a place in the household of Charles I, Margrave of Baden, and soon, having some reputation as a Latinist, he was chosen to accompany Frederick, the third son of the prince, to the University of Paris. Frederick was some years his junior, and was destined for an ecclesiastical career. This new connection did not last long, but it determined the course of Reuchlin's life. He now began to learn Greek, which had been taught in the French capital since 1470, and he also attached himself to the leader of the Paris realists, Jean à Lapide (d. 1496), a worthy and learned man, whom he followed to the vigorous young University of Basel in 1474.
At Basel Reuchlin took his master's degree (1477), and began to lecture with success, teaching a more classical Latin than was then common in German schools, and explaining Aristotle in Greek. His studies in this language had been continued at Basel under Andronicus Contoblacas, and here he formed the acquaintance of the bookseller, Johann Amerbach, for whom he prepared a Latin lexicon (Vocabularius Breviloquus, 1st ed, 1475–76), which ran through many editions. This first publication, and Reuchlin's account of his teaching at Basel in a letter to Cardinal Adrian (Adriano Castellesi) in February 1518, show that he had already found his life's work. He was a born teacher, and this work was not to be done mainly from the professor's chair.
Reuchlin soon left Basel to seek further Greek training with George Hermonymus at Paris, and to learn to write a fair Greek hand that he might support himself by copying manuscripts. And now he felt that he must choose a profession. His choice fell on law, and he was thus led to the great school of Orléans (1478), and finally to Poitiers, where he became licentiate in July 1481. From Poitiers Reuchlin went in December 1481 to Tübingen with the intention of becoming a teacher in the local university, but his friends recommended him to Count Eberhard of Württemberg, who was about to journey to Italy and required an interpreter. Reuchlin was selected for this post, and in February 1482 left Stuttgart for Florence and Rome. The journey lasted but a few months, but it brought the German scholar into contact with several learned Italians, especially at the Medicean Academy in Florence; his connection with the count became permanent, and after his return to Stuttgart he received important posts at Eberhard's court.
About this time he appears to have married, but little is known of his married life. He left no children; but in later years his sister's grandson Philipp Melanchthon was like a son to him till the Reformation estranged them. In 1490 he was again in Italy. Here he saw Pico della Mirandola, to whose Cabbalistic doctrines he afterwards became heir, and made a friend of the pope's secretary, Jakob Questenberg, which was of service to him in his later troubles. Again in 1492 he was employed on an embassy to the emperor Frederick at Linz, and here he began to read Hebrew with the emperor's Jewish physician Jakob ben Jehiel Loans. Loans's instruction laid the basis of that thorough knowledge which Reuchlin afterwards improved on his third visit to Rome in 1498 by the instruction of Obadja Sforno of Cesena. In 1494 his rising reputation had been greatly enhanced by the publication of De Verbo Mirifico.