Piero (also Perino, Pietro) Tomacelli came of an ancient but impoverished baronial family of Naples. An unsympathetic German contemporary source, Dietrich of Nieheim, asserted that he was illiterate (nesciens scribere etiam male cantabat); neither a trained theologian nor skilled in the business of the Curia, he was tactful and prudent in a difficult era, but Ludwig Pastor, who passes swiftly over his pontificate, says, "The numerous endeavours for unity made during this period form one of the saddest chapters in the history of the Church. Neither Pope had the magnanimity to put an end to the terrible state of affairs" by resigning. Germany, England, Hungary, Poland, and the greater part of Italy accepted him as pope, (he and the Avignon Pope Clement VII having mutually excommunicated one another) but the day before Tomacelli's election by the fourteen cardinals who remained faithful to the papacy at Rome, Clement VII at Avignon had just crowned a French prince, Louis II of Anjou, King of Naples. The youthful Ladislaus was rightful heir of Charles III of Naples, assassinated in 1386, and Margaret of Durazzo, scion of a line that had traditionally supported the popes in their struggles in Rome with the anti-papal party in the city itself. Boniface IX saw to it that Ladislaus was crowned King of Naples at Gaeta May 29, 1390) and worked with him for the next decade to expel the Angevin forces from southern Italy.
In the course of his reign Boniface IX finally extinguished the troublesome independence of the commune of Rome and established temporal control, though it required fortifying not only the Castel Sant'Angelo, but the very bridges, and for long seasons he was forced to reside in more peaceful surroundings, at Assisi or Perugia. He also took over the port of Ostia from its Cardinal Bishop. In the Papal States Boniface IX gradually regained control of the chief castles and cities, and he re-founded the States as they would appear during the fifteenth century.
Clement VII died at Avignon, September 16, 1394, but the French cardinals quickly elected a successor, on September 28: Cardinal Pedro de Luna, who took the name Benedict XIII (1394—1423). Over the next few years Boniface IX was entreated to abdicate, even by his strongest supporters: Richard II of England (in 1396), the Diet of Frankfurt (in 1397), and King Wenceslaus of Germany (at Reims, 1398). But he refused. Pressure for an ecumenical council also grew as the only way to breach the Great Schism, but the conciliar movement made no headway during Boniface IX's papacy.
During the reign of Boniface IX two jubilees were celebrated at Rome. The first, in 1390, had been declared by his predecessor Pope Urban VI, and was largely frequented by people from Germany, Hungary, Poland, Bohemia, and England. Several cities of Germany obtained the "privileges of the jubilee", as indulgences were called, but the preaching of indulgences gave rise to abuses and scandal. The jubilee of 1400 drew to Rome great crowds of pilgrims, particularly from France, in spite of a disastrous plague. Pope Boniface IX remained in the city.
In the latter part of 1399 there arose bands of self-flagellating penitents, known as the Bianchi, or Albati ("White Penitents"), especially in Provence, where the Albigenses had been exterminated less than a century before, and spreading to Spain and northern Italy. These evoked uneasy memories of the mass processions of wandering flagellants of the Black Death period, 1348—1349. They went in procession from city to city, clad in white garments, with faces hooded, and wearing on their backs a red cross, following a leader who carried a large cross. Rumors of imminent divine judgement and visions of the Virgin Mary abounded. They sang the newly popular hymn Stabat Mater during their processions. For a while, as the White Penitents approached Rome, gaining adherents along the way, Boniface IX and the Curia supported their penitential enthusiasm, but when they reached Rome, Boniface IX had their leader burnt at the stake, and they soon dispersed. "Boniface IX gradually discountenanced these wandering crowds, an easy prey of agitators and conspirators, and finally dissolved them." as the Catholic Encyclopedia reports.
In England the anti-papal preaching of John Wyclif supported the opposition of the King and the higher clergy to Boniface IX's habit of granting English benefices as they fell vacant to favorites in the Roman Curia. Boniface IX introduced a novelty in the form of revenue known as annates perpetuæ, withholding half the first year's income of every benefice granted in the Roman Court. The pope's agents also now sold not simply a vacant benefice but the expectation of one; and when an expectation had been sold, if another offered a larger sum for it, the pope voided the first sale; the unsympathetic observer Dietrich von Nieheim reports that he saw the same benefice sold several times in one week, and that the Pope talked business with his secretaries during Mass. There was resistance in England, the staunchest supporter of the Roman papacy during the Schism: the English Parliament confirmed and extended the statutes of Provisors and Præmunire of Edward III of England (1327–77), giving the king veto power over papal appointments in England. Boniface IX was defeated in the face of a unified front, and the long controversy was finally settled, to the English king's satisfaction. Nevertheless, at the Synod of London (1396), the English bishops convened to condemn Wyclif.
In Germany the Electors had met at Rhense (August 20, 1400) to depose the unworthy Wenceslaus, and had chosen in his place Rupert, Duke of Bavaria and Rhenish Count Palatine. In 1403 Boniface IX made the best of it and approved the deposition and recognized Rupert.
In 1398 and 1399 Boniface IX appealed to Christian Europe in favor of the Byzantine emperor Manuel II Palaeologus, threatened at Constantinople by Sultan Bayezid I, but there was little enthusiasm for a new crusade at such a time. Saint Birgitta of Sweden was canonized by Pope Boniface IX, October 7, 1391. The universities of Ferrara (1391) and Fermo (1398) owe him their origin, and that of Erfurt (in Germany), its confirmation (1392).
Boniface IX died in 1404 after a brief illness.
Boniface IX was a frank politician, strapped for cash like the other princes of Europe, as the costs of modern warfare rose and supporters needed to be encouraged by gifts, for [fourteenth-century government depended upon such personal support as a temporal ruler could gather and retain. All of the princes of the late fourteenth century were accused of avaricious money-grubbing by contemporary critics, but among them contemporaries ranked Boniface IX exceptional. Traffic in benefices, the sale of dispensations, and the like, did not cover the loss of local sources of revenue in the long absence of the papacy from Rome, foreign revenue diminished by the schism, expenses for the pacification and fortification of Rome, the constant wars necessitated by French ambition and the piecemeal reconquest of the Papal States. Boniface IX certainly provided generously for his mother, his brothers Andrea and Giovanni, and his nephews in the spirit of the day. The Curia was perhaps equally responsible for new financial methods that were destined in the next century to arouse bitter feelings against Rome, particularly in Germany.
(Note on numbering: Pope Boniface VII is now considered an anti-pope. At the time however, this fact was not recognized and so the seventh true Pope Boniface took the official number VIII. This caused the true eighth Pope Boniface to take the number IX. This has advanced the numbering of all subsequent Popes Boniface by one. Popes Boniface VIII-IX are really the seventh through eight popes by that name.)