From an early age, he was destined for an ecclesiastical career. He received the tonsure at the age of seven and was soon loaded with rich benefices and preferments. His father prevailed on his relative Innocent VIII to name him cardinal deacon of Santa Maria in Domnica on March 8, 1489, although he was not allowed to wear the insignia or share in the deliberations of the college until three years later. Meanwhile he received a distinguished education at Lorenzo's brilliant humanistic court under such men as Angelo Poliziano, Pico della Mirandola, Marsilio Ficino and Bernardo Dovizio Bibbiena. From 1489 to 1491 he studied theology and canon law at Pisa under Filippo Decio and Bartolomeo Sozzini.

On 23 March 1492, he was formally admitted into the Sacred College and took up his residence at Rome, receiving a letter of advice from his father. The death of Lorenzo on the following April 8, however, called the 16 year old cardinal to Florence. He participated in the conclave of 1492 which followed the death of Innocent VIII, and unsuccessfully opposed the election of Cardinal Borgia. He made his home with his elder brother Piero at Florence throughout the agitation of Savonarola and the invasion of Charles VIII of France, until the uprising of the Florentines and the expulsion of the Medici in November 1494. While Piero found refuge at Venice and Urbino, Cardinal Giovanni traveled in Germany, in the Netherlands and in France.

In May 1500, he returned to Rome, where he was received with outward cordiality by Pope Alexander VI, and where he lived for several years immersed in art and literature. In 1503 he welcomed the accession of Pope Julius II to the pontificate; the death of Piero de' Medici in the same year made Giovanni head of his family. On 1 October 1511 he was appointed papal legate of Bologna and the Romagna, and when the Florentine republic declared in favor of the schismatic Pisans, Julius II sent him against his native city at the head of the papal army. This and other attempts to regain political control of Florence were frustrated, until a bloodless revolution permitted the return of the Medici. Giovanni's younger brother Giuliano was placed at the head of the republic, but the cardinal managed the government.

Giovanni was elected Pope on 9 March 1513, and this was proclaimed two days later. On the 15 March he was ordained priest, and consecrated as bishop on the 17th. He was crowned Pope on 19 March at the age of 37.

At the very time of Leo's accession Louis XII of France, in alliance with Venice, was making a determined effort to regain the duchy of Milan, and Leo, after fruitless endeavors to maintain peace, joined the league of Mechlin on 5 April 1513 with the emperor Maximilian I, Ferdinand II of Aragon and Henry VIII of England. The French and Venetians were at first successful, but were defeated in June at the Battle of Novara. The Venetians continued the struggle until October. On 9 December the fifth Lateran council, which had been reopened by Leo in April, ratified the peace with Louis XII and officially registered the conclusion of the Pisan schism.

While the council was engaged in planning a crusade and in considering the reform of the clergy, a new crisis occurred between the pope and the new king of France, Francis I, an enthusiastic young prince, dominated by the ambition of recovering Milan and the Kingdom of Naples. Leo at once formed a new league with the emperor and the king of Spain, and to ensure English support made Thomas Wolsey a cardinal.

Francis entered Italy in August and on 14 September won the battle of Marignano. In October Leo signed an agreement binding him to withdraw his troops from Parma and Piacenza, which had been previously gained at the expense of the duchy of Milan, on condition of French protection at Rome and Florence. The king of Spain wrote to his ambassador at Rome "that His Holiness had hitherto played a double game and that all his zeal to drive the French from Italy had been only a mask"; this reproach seemed to receive some confirmation when Leo held a secret conference with Francis at Bologna in December 1515. The ostensible subjects under consideration were the establishment of peace between France, Venice and the Empire, with a view to an expedition against the Turks, and the ecclesiastical affairs of France. Precisely what was arranged is unknown.

During these two or three years of incessant political intrigue and warfare it was not to be expected that the Lateran council should accomplish much. Its three main objectives, the peace of Christendom, the crusade (against the Turks), and the reform of the church, could be secured only by general agreement among the powers, and either Leo or the council, or both, failed to secure such agreement.

Its most important achievements were the registration at its eleventh sitting (9 December 1516) of the abolition of the pragmatic sanction, which the popes since Pius II had unanimously condemned, and the confirmation of the concordat between Leo X and Francis I, which was destined to regulate the relations between the French Church and the Holy See until the French Revolution. Leo closed the council on 16 March 1517. It had ended the Pisan schism, ratified the censorship of books introduced by Alexander VI and imposed tithes for a war against the Turks. It raised no voice against the primacy of the pope.

Leo had intended his younger brother Giuliano and his nephew Lorenzo for brilliant secular careers. He had named them Roman patricians; the latter he had placed in charge of Florence; the former, for whom he planned to carve out a kingdom in central Italy of Parma, Piacenza, Ferrara and Urbino, he had taken with himself to Rome and married to Filiberta of Savoy.

The death of Giuliano in March 1516, however, caused the pope to transfer his ambitions to Lorenzo. At the very time (December 1516) that peace between France, Spain, Venice and the Empire seemed to give some promise of a Christendom united against the Turks, Leo was preparing an enterprise as unscrupulous as any of the exploits of Cesare Borgia. He obtained 150,000 ducats towards the expenses of the expedition from Henry VIII of England, in return for which he entered the imperial league of Spain and England against France.

The war lasted from February to September 1517 and ended with the expulsion of the duke and the triumph of Lorenzo; but it revived the allegedly nefarious policy of Alexander VI, increased brigandage and anarchy in the Papal States, hindered the preparations for a crusade and wrecked the papal finances. Francesco Guicciardini reckoned the cost of the war to Leo at the prodigious sum of 800,000 ducats. But ultimately Lorenzo was confirmed as the new duke of Urbino.

The war of Urbino was further marked by a crisis in the relations between pope and cardinals. The sacred college had allegedly grown especially worldly and troublesome since the time of Sixtus IV, and Leo took advantage of a plot of several of its members to poison him, not only to inflict exemplary punishments by executing one and imprisoning several others, but also to make a radical change in the college.

On 3 July 1517 he published the names of thirty - one new cardinals, a number almost unprecedented in the history of the papacy. Among the nominations were such notable men such as Lorenzo Campeggio, Giambattista Pallavicini, Adrian of Utrecht, Thomas Cajetan, Cristoforo Numai and Egidio Canisio. The naming of seven members of prominent Roman families, however, reversed the policy of his predecessor which had kept the political factions of the city out of the Curia. Other promotions were for political or family considerations or to secure money for the war against Urbino. The pope was accused of having exaggerated the conspiracy of the cardinals for purposes of financial gain, but most of such accusations appear unsubstantiated.

Leo, meanwhile, felt the need of staying the advance of the Ottoman sultan, Selim I, who was threatening western Europe, and made elaborate plans for a crusade. A truce was to be proclaimed throughout Christendom; the pope was to be the arbiter of disputes; the emperor and the king of France were to lead the army; England, Spain and Portugal were to furnish the fleet; and the combined forces were to be directed against Constantinople. Papal diplomacy in the interests of peace failed, however; Cardinal Wolsey made England, not the pope, the arbiter between France and the Empire; and much of the money collected for the crusade from tithes and indulgences was spent in other ways.

In 1519 Hungary concluded a three years' truce with Selim I, but the succeeding sultan, Suleyman the Magnificent, renewed the war in June 1521 and on 28 August captured the citadel of Belgrade. The pope was greatly alarmed, and although he was then involved in war with France he sent about 30,000 ducats to the Hungarians.

Leo treated the Uniate Greeks with great loyalty, and by bull of 18 May 1521 forbade Latin clergy to celebrate mass in Greek churches and Latin bishops to ordain Greek clergy. These provisions were later strengthened by Clement VII and Paul III and went far to settle the constant disputes between the Latins and Uniate Greeks.

Leo was disturbed throughout his pontificate by schism, especially the Reformation sparked by Martin Luther.

In response to concerns about misconduct from some servants of the church, in 1517 Martin Luther read his Ninety - Five Theses on the topic of indulgences in the church courtyard at Wittenberg. Students took the theses, translated them from Latin to German, and through the printing press they spread throughout Europe. Within two weeks, the theses had spread throughout Germany, and after two months they had spread throughout Europe. Leo failed to fully comprehend the importance of the movement, and in February 1518 he directed the vicar general of the Augustinians to impose silence on his monks.

On 30 May, Luther sent an explanation of his theses to the pope; on 7 August he was summoned to appear at Rome. An arrangement was effected, however, whereby that summons was cancelled, and Luther went instead to Augsburg in October 1518 to meet the papal legate, Cardinal Cajetan; but neither the arguments of the cardinal, nor Leo's dogmatic papal bull of 9 November requiring all Christians to believe in the pope's power to grant indulgences, moved Luther to retract. A year of fruitless negotiations followed, during which the controversy took popular root across the German States.

A further papal bull of 15 June 1520, Exsurge Domine or Arise, O Lord, condemned forty - one propositions extracted from Luther's teachings, and was taken to Germany by Eck in his capacity as apostolic nuncio. Leo followed by formally excommunicating Luther by the bull Decet Romanum Pontificem or It Pleases the Roman Pontiff, on 3 January 1521. In a brief the Pope also directed Charles V, Holy Roman Emperor to take energetic measures against heresy.

It was also under Leo that Lutheranism spread into Scandinavia. The pope had repeatedly used the rich northern benefices to reward members of the Roman curia, and towards the close of the year 1516 he sent the impolitic Arcimboldi as papal nuncio to Denmark to collect money for St Peter's. This led to the Reformation in Denmark - Norway and Holstein. King Christian II took advantage of the growing dissatisfaction of the native clergy toward the papal government, and of Arcimboldi's interference in the Swedish revolt, to expel the nuncio and summon Lutheran theologians to Copenhagen in 1520. Christian approved a plan by which a formal state church should be established in Denmark, all appeals to Rome should be abolished, and the king and diet should have final jurisdiction in ecclesiastical causes. Leo sent a new nuncio to Copenhagen (1521) in the person of the Minorite Francesco de Potentia, who readily absolved the king and received the rich bishopric of Skara. The pope or his legate, however, took no steps to remove abuses or otherwise reform the Scandinavian churches.

That Leo did not do more to check the anti - papal rebellion in Germany and Scandinavia is to be partially explained by the political complications of the time, and by his own preoccupation with papal and Medicean politics in Italy. The death of the emperor Maximilian in 1519 had seriously affected the situation. Leo vacillated between the powerful candidates for the succession, allowing it to appear at first that he favored Francis of a minor German prince. He finally accepted Charles V of Spain as inevitable, and the election of Charles (28 June 1519) revealed Leo's desertion of his French alliance.

Leo was now eager to unite Ferrara, Parma and Piacenza to the States of the Church (The Papal States). An attempt late in 1519 to seize Ferrara failed, and the pope recognized the need for foreign aid. In May 1521 a treaty of alliance was signed at Rome between him and the emperor. Milan and Genoa were to be taken from France and restored to the Empire, and Parma and Piacenza were to be given to the Church on the expulsion of the French. The expense of enlisting 10,000 Swiss was to be borne equally by pope and emperor. Charles V took Florence and the Medici family under his protection and promised to punish all enemies of the Catholic faith. Leo agreed to invest Charles V with the Kingdom of Naples, to crown him Holy Roman Emperor, and to aid in a war against Venice. It was provided that England and the Swiss might also join the league. Henry VIII announced his adherence in August 1521. Francis I had already begun war with Charles V in Navarre, and in Italy, too, the French made the first hostile movement on June 23, 1521. Leo at once announced that he would excommunicate the king of France and release his subjects from their allegiance unless Francis I laid down his arms and surrendered Parma and Piacenza to the Church. The pope lived to hear the joyful news of the capture of Milan from the French and of the occupation by papal troops of the long coveted provinces (November 1521).

Having fallen ill with malaria, Pope Leo X died on December 1, 1521, so suddenly that the last sacraments could not be administered; but the contemporary suspicions of poison were unfounded. He was buried in Santa Maria sopra Minerva.

In the past many conflicting estimates were made of the character and achievements of the pope during whose pontificate Protestantism first took form. More recent studies have served to produce a reportedly fairer and more honest opinion of Leo X. A report of the Venetian ambassador Marino Giorgi bearing the date of March 1517 indicates some of his predominant characteristics:

The pope is a good - natured and extremely free - hearted man, who avoids every difficult situation and above all wants peace; he would not undertake a war himself unless forced into it by his advisors; he loves learning; of canon law and literature he possesses remarkable knowledge; he is, moreover, a very excellent musician.

Leo X held a demeanor that won the affection and support of many. So much so, that he was later elected pope without much resistance. Although, he was taken with intellectual and cultural pursuits, he had no greater priority in his pontificate than maintaining peace. With reference to his other virtues, Ludovico Pastor comments that “the joyful humor, celebrated by all his contemporaries, never left the Pope, even amidst the multiple nightmares that the dispositions of his weakened health implied.”

Leo X’s love for all forms of art stemmed from the humanistic education he received in Florence, his studies in Pisa and his extensive travel throughout Europe. He loved the Latin poems of the humanists, the tragedies of the Greeks or the Livian comedies of Bibbiena and Ariosto, while still following the accounts from the explorers of the New World. Yet “Such a humanistic interest was itself religious…. In the Renaissance, the vines of the classical world and the Christian world, of Rome, were seen as intertwined. It was a historically minded culture where artists’ representations of Cupid and the Madonna, of Hercules and St. Peter could exist side - by - side.”

Several modern historians have concluded that Leo was homosexual. Contemporary tracts and accounts such as that of Francesco Guicciardini have been found to allude to active same - sex relations – alleging Count Ludovico Rangone and Galeotto Malatesta among his lovers.

Cesare Falconi has examined in particular Leo's infatuation with the Venetian noble Marcantonio Flaminio, with Leo arranging the best education that could be offered for the time. Von Pastor has argued, however, against the credibility of these testimonies, and rejected accusations of immorality as anti - papal polemic. Gucciardini was not resident at the papal court during Leo's pontificate, while other contemporaries such as Matteo Herculano took pains to praise his chastity. Paul Strathern, a British writer and academic, argues that Leo while homosexual, was not sexually active as pope, despite identifying notable members of that family as such.

When he became pope, Leo X is reported to have said to his brother Giuliano: "Since God has given us the Papacy, let us enjoy it." The Venetian ambassador who related this of him was not unbiased, nor was he in Rome at the time, nevertheless the phrase illustrates fairly the Pope's culture loving nature and the humanistic interests that characterized him. And enjoy he did, traveling around Rome at the head of a lavish parade featuring panthers, jesters, and Hanno, a white elephant.

Under his pontificate, Latin Christianity assumed a pagan, Greco - Roman character, which, passing from art into manners, gives to this epoch a strange complexion. Crimes for the moment disappeared, to give place to vices; but to charming vices, vices in good taste, such as those indulged in by Alcibiades and sung by Catullus. Alexandre Dumas, père

Leo X was also lavish in charity: retirement homes, hospitals, convents, discharged soldiers, pilgrims, poor students, exiles, cripples and the sick, unfortunates of every description were generously remembered, and more than 6,000 ducats were annually distributed in alms. As a patron of learning Leo X deserves a prominent place among the popes. He raised the Church to a high rank as the friend of whatever seemed to extend knowledge or to refine and embellish life. He made the capital of Christendom, Rome, the center of European culture. While yet a cardinal, he had restored the church of Santa Maria in Domnica after Raphael's designs; and as pope he had San Giovanni dei Fiorentini, on the Via Giulia, built, after designs by Jacopo Sansovino and pressed forward the work on St Peter's Basilica and the Vatican under Raphael and Agostino Chigi.

Leo's constitution of 5 November 1513 reformed the Roman university, which had been neglected by Julius II. He restored all its faculties, gave larger salaries to the professors, and summoned distinguished teachers from afar; and, although it never attained to the importance of Padua or Bologna, it nevertheless possessed in 1514 a faculty (with a good reputation) of eighty - eight professors.

Leo called Janus Lascaris to Rome to give instruction in Greek, and established a Greek printing - press from which the first Greek book printed at Rome appeared in 1515. He made Raphael custodian of the classical antiquities of Rome and the vicinity. The distinguished Latinists Pietro Bembo and Jacopo Sadoleto were papal secretaries, as well as the famous poet Bernardo Accolti.

Other poets such as Marco Girolamo Vida, Gian Giorgio Trissino and Bibbiena, writers of novelle like Matteo Bandello, and a hundred other literati of the time were bishops, or papal scriptors or abbreviators, or in other papal employ.

Leo's lively interest in art and literature, to say nothing of his natural liberality, his alleged nepotism, his political ambitions and necessities, and his immoderate personal luxury, exhausted within two years the hard savings of Julius II, and precipitated a financial crisis from which he never emerged and which was a direct cause of most of what, from a papal point of view, were calamities of his pontificate.

He sold cardinals' hats. He sold membership in the "Knights of Peter". He borrowed large sums from bankers, curials, princes and Jews. The Venetian ambassador Gradenigo estimated the paying number of offices on Leo's death at 2,150, with a capital value of nearly 3,000,000 ducats and a yearly income of 328,000 ducats.

The ordinary income of the pope for the year 1517 had been reckoned at about 580,000 ducats, of which 420,000 came from the States of the Church, 100,000 from annates, and 60,000 from the composition tax instituted by Sixtus IV. These sums, together with the considerable amounts accruing from indulgences, jubilees, and special fees, vanished as quickly as they were received. Then the pope resorted to pawning palace furniture, table plate, jewels, even statues of the apostles. Several banking firms and many individual creditors were ruined by the death of Leo.

Several minor events of Leo's pontificate are worthy of mention. He was particularly friendly with King Manuel I of Portugal as a result of the latter's missionary enterprises in Asia and Africa. His concordat with Florence (1516) guaranteed the free election of the clergy in that city.

His constitution of 1 March 1519 condemned the king of Spain's claim to refuse the publication of papal bulls. He maintained close relations with Poland because of the Turkish advance and the Polish contest with the Teutonic Knights. His bull of July 1519, which regulated the discipline of the Polish Church, was later transformed into a concordat by Clement VII.

Leo showed special favors to the Jews and permitted them to erect a Hebrew printing press at Rome.

He approved the formation of the Oratory of Divine Love, a group of pious men at Rome which later became the Theatine Order, and he canonized Francis of Paola.