He was educated at Rome, attending the classes of eminent professors, among them Leonardi Bruni and Giovanni Aurispa (c. 1369-1459), from whom he learned Latin and Greek. In 1431 he became a priest, and after trying vainly to secure a position as apostolic secretary in Rome he went to Piacenza, whence he proceeded to Pavia, where he obtained a professorship of eloquence. Valla wandered from one university to another, accepting short engagements and lecturing in many cities. During this period he made the acquaintance of Alphonso V of Aragon, whose service he entered about 1435. Alphonso made Valla his private secretary, defended him against the attacks of his numerous enemies, and at a later date encouraged him to open a school in Naples.
By this time Valla had won a high reputation by his dialogue De Voluptate, and by his treatise De Elegantiis Latinae Linguae. In the former work he contrasted the principles of the Stoics with the tenets of Epicurus, openly proclaiming his sympathy with those who claimed the right of free indulgence for man's natural appetites. It was a remarkable utterance. Here for the first time the paganismism of the Renaissance found deliberate expression in a work of scholarly and philosophical value. De Elegantiis was no less original, although in a different sphere of thought. This work subjected the forms of Latin grammar and the rules of Latin style and rhetoric to a critical examination, and placed the practice of composition upon a foundation of analysis and inductive reasoning. The same originality and critical acumen were displayed in his treatise on the Donation of Constantine (De falso credita et ementita Constantini donatione declamatio), written in 1439 during the pontificate of Eugenius IV, in which the nature of the forged document known as the Constitutum Constantini was for the first time exposed.
From Naples Valla continued his war against the Church. He showed that the supposed letter of Christ to Abgarus was a forgery, and by throwing doubt upon the authenticity of other spurious documents, and by questioning the utility of monastic life, he aroused the anger of the faithful. He was compelled to appear before an inquisitory tribunal composed of his enemies, and he only escaped by the special intervention of Alphonso. He was not, however, silenced; he ridiculed the Latin of the Vulgate and accused St Augustine of heresy. In 1444 he visited Rome, but in this city also his enemies were numerous and powerful, and he only saved his life by flying in disguise to Barcelona, whence he returned to Naples. But a better fortune attended him after the death of Eugenius IV in February 1447. Again he journeyed to Rome, where he was welcomed by the new pope, Nicholas V, who made him an apostolic secretary, and this entrance of Valla into the Roman Curia has been justly called "the triumph of humanism over orthodoxy and tradition." Valla also enjoyed the favour of Pope Calixtus III.
All the older biographical notices of Valla are loaded with long accounts of his many literary and theological disputes, the most famous of which was the one with Poggio, which took place after his settlement in Rome. It is almost impossible to form a just estimate of Valla's private life and character owing to the clouds of dust which were stirred up by this and other controversies, in which the most virulent and obscene language was employed. He appears, however, as a vain, jealous and quarrelsome man, but he combined the qualities of an elegant humanist, an acute critic and a venomous writer, who had committed himself to a violent polemic against the temporal power of Rome. In him posterity honours not so much the scholar and the stylist as the man who initiated a bold method of criticism, which he applied alike to language, to historical documents and to ethical opinions. Luther had a very high opinion of Valla and of his writings, and Cardinal Bellarmine calls him praecursor Lutheri, while Sir Richard Jebb says that his De Elegantiis "marked the highest level that had yet been reached in the critical study of Latin."
Collected, but not quite complete, editions of Valla's works were published at Basel in 1540 and at Venice in 1592 fol., and De Elegantiis was reprinted nearly sixty times between 1471 and 1536. For detailed accounts of Valla's life and work see G Voigt, Die Wiederbelebung des classischen Alterthums (1880-81); JA Symonds, Renaissance in Italy (1897-99); G Mancini, Vita di Lorenzo Valla (Florence, 1891); M. von Wolff, Lorenzo Valla (Leipzig, 1893); Jakob Burckhardt, Kultur der Renaissance (1860); J Vahlen, Laurentius Valla (Berlin, 1870); L Pastor, Geschichte der Päpste, Band ii. English trans. by FI Antrobus (1892); the article in Herzog-Hauck's Realencyklopädie, Band xx. (Leipzig, 1908); and JE Sandys, Hist. of Class. Schol. ii. (1908), pp. 66-70.