Benvenuto Cellini was born in Florence, Italy. His parents were Giovanni Cellini, and Maria Lisabetta Granacci. They were married for eighteen years before the birth of their first child. Benvenuto was the second child of the family. The son of a musician and builder of musical instruments, Cellini's first major brush with the law came as an early teenager: He was banished from his native Florence for his alleged role in a brawl. As a result, he received his early artistic training not only from the Florentine goldsmith Marcone [Antonio di Sandro], but also from Francesco Castoro, a goldsmith of Siena. After further visits to Bologna and Pisa, Cellini was allowed to return to Florence and continue his work there.

Giovanni initially wished Benvenuto to join him in instrument making, and endeavoured to thwart his inclination for metalwork. When he was fifteen, his father reluctantly agreed to apprentice him to a goldsmith, Antonio di Sandro, nicknamed Marcone. At the age of sixteen, Benvenuto had already attracted attention in Florence by taking part in an affray with youthful companions. He escaped punishment by fleeing for six months to Siena, where he worked for a goldsmith named Fracastoro (unrelated to the Veronese polymath). From Siena he moved to Bologna, where he became a more accomplished flute player and made progress as a goldsmith. After a visit to Pisa and two periods of living in Florence (where he was visited by the sculptor Torrigiano), he moved to Rome, age nineteen.

His first works in Rome were a silver casket, silver candlesticks, and a vase for the bishop of Salamanca, which won him the approval of Pope Clement VII. Another celebrated work from Rome is the gold medallion of "Leda and the Swan" executed for the Gonfaloniere Gabbriello Cesarino, and which is now in the Vienna museum. He also took up the flute again, and was appointed one of the pope's court musicians. In the attack upon Rome by Charles III, Duke of Bourbon, Cellini's bravery proved of signal service to the pontiff. According to his own accounts, he himself shot and injured Philibert of Châlon, prince of Orange. (Allegedly Cellini also killed Charles III, Duke of Bourbon during the Siege of Rome.) His bravery led to a reconciliation with the Florentine magistrates, and he soon returned to his hometown. Here he devoted himself to crafting medals, the most famous of which are "Hercules and the Nemean Lion", in gold repoussé work, and "Atlas supporting the Sphere", in chased gold, the latter eventually falling into the possession of Francis I of France.

From Florence he went to the court of the duke of Mantua, and then again to Florence. On returning to Rome, he was employed in the working of jewellery and in the execution of dies for private medals and for the papal mint. In 1529 his brother Cecchino killed a Corporal of the Roman Watch and in turn was wounded by an arquebusier, later dying of his wound. Soon afterward Benvenuto killed his brother's killer – an act of blood revenge but not justice as Cellini admits that his brother's killer had acted in self-defense. Cellini fled to Naples to shelter from the consequences of an affray with a notary, Ser Benedetto, whom he had wounded. Through the influence of several cardinals, Cellini obtained a pardon. He found favor with the new pope,Paul III, notwithstanding a fresh homicide during the interregnum three days after the death of Pope Clement VII in September 1534. The fourth victim was a rival goldsmith who was working under Cellini's employment; Pompeo of Milan. Cellini reported in his autobiography that he had fallen in love with Pompeo and admired watching his magnificent physique as he worked near the furnace melting iron and bronze, and that he bore the hope of his affections to soon be acknowledged and returned by Pompeo. When Cellini learned that Pompeo was absent from work that day as his wife's lover, he admitted to visiting the Villa where his separated wife lived and meeting Pompeo at the door, stabbed him on the threshold. His wife he immediately stabbed afterward inside of the home for her 'betrayal'. The killings, the fourth and fifth that Cellini boasts of in his memoirs, was reported in his autobiography as nothing more than a 'justifiable accident during a heated argument' rather than by premeditated malice. He was saved from arrest only because of a safe-conduct by the Pope.

The plots of Pierluigi Farnese led to Cellini's retreat from Rome to Florence and Venice, where he was restored with greater honour than before. At the age of 37, upon returning from a visit to the French court, he was imprisoned on a charge (apparently false) of having embezzled during the war the gems of the pope's tiara. He was confined in the Castel Sant' Angelo, escaped, was recaptured, and treated with great severity, and was in daily expectation of death on the scaffold. The intercession of Pierluigi's wife, and especially that of the Cardinal d'Este of Ferrara, eventually secured Cellini's release, in gratitude for which he gave d'Este a splendid cup.

Cellini then worked at the court of Francis I at Fontainebleau and Paris. However, he considered the duchesse d'Étampes to be set against him and refused to conciliate with the king's favorites. He could no longer silence his enemies by the sword, as he had silenced those in Rome. As a result, after about five years of invested work but continual jealousy and violence, Cellini returned to Florence, where he continued as a goldsmith and became the rival of sculptor Baccio Bandinelli, who died a few years later in 1560. During the war with Siena, Cellini was appointed to strengthen the defences of his native city, and, though rather shabbily treated by his ducal patrons, he continued to gain the admiration of his fellow citizens by the magnificent works which he produced. He was also named a member (Accademico) of the prestigious Accademia delle Arti del Disegno of Florence, founded by the Duke Cosimo I de' Medici, at 13 January 1563, under the influence of the architect Giorgio Vasari. He died in Florence in 1571 and was buried with great pomp in the church of the Santissima Annunziata. He had supported in Florence a widowed sister and her six daughters.

Cellini is known to have taken some of his female models as mistresses, having an illegitimate daughter in 1544 with one of them while living in France, whom he named Costanza. After briefly attempting a clerical career, in 1562, he married a servant, Piera Parigi, with whom he claimed he had five children, of which only a son and two daughters survived him. Outside his marriage, Cellini was officially charged or accused three times with homosexual sodomy and once with heterosexual.

• 14 January 1523 he was sentenced to pay 12 staia of flour for relations with a boy named Domenico di ser Giuliano da Ripa.
• While in Paris, a former model and lover brought charges against him of using her "after the Italian fashion."
• In Florence in 1548, Cellini was accused by a woman named Margherita, for having certain familiarities with her son, Vincenzo.
• 26 February 1556, his apprentice Fernando di Giovanni di Montepulciano accused his mentor of having sodomised him many times. This time the penalty was a hefty fifty golden scudi fine, and four years of prison, remitted to four years of house arrest thanks to the intercession of the Medicis.

Towards the end of his life during a public altercation before Duke Cosimo, Bandinelli had called out to him Sta cheto, soddomitaccio! (Shut up, you filthy sodomite!) Cellini qualified it an "atrocious insult."

Besides his works in gold and silver, Cellini executed sculptures of grander scale. The most distinguished of these is the bronze group of Perseus with the Head of Medusa, a work (first suggested by Duke Cosimo I de Medici) now in the Loggia dei Lanzi at Florence, his attempt to surpass Michelangelo's David and Donatello's Judith and Holofernes. The casting of this work caused Cellini much trouble and anxiety, but it was hailed as a masterpiece as soon as it was completed. The original relief from the foot of the pedestal — Perseus and Andromeda — is in the Bargello, and replaced by a cast. By 1996, centuries of environmental pollution exposure had streaked and banded the statue. In December of that year it was removed from the Loggia and transferred to the Uffizi for cleaning and restoration. It was a slow, years long process, and the restored statue was not returned to its home until June 2000.

Among his art works, many of which have perished, were a colossal Mars for a fountain at Fontainebleau and the bronzes of the doorway, coins for the Papal and Florentine states, a life-sized silver Jupiter, and a bronze bust of Bindo Altoviti. The works of decorative art are florid in style.

In addition to the bronze statue of Perseus and the medallions already referred to, the works of art in existence today are a medallion of Clement VII commemorating the peace between the Christian princes, 1530, with a bust of the pope on the reverse and a figure of Peace setting fire to a heap of arms in front of the temple of Janus, signed with the artist's name; a signed portrait medal of Francis; a medal of Cardinal Pietro Bembo; and the celebrated gold, enamel and ivory salt cellar (known as Saliera) made for Francis I of France at Vienna. This intricate 26 cm-high sculpture, of a value conservatively estimated at 58,000,000 schilling, was commissioned by Francis I. Its principal figures are a naked sea god and a woman sitting opposite each other with legs entwined, symbolically representing the planet Earth. "Saliera" was stolen from the Kunsthistorisches Museum on 11 May 2003 by a thief who climbed a scaffolding and smashed the windows to enter the museum. The thief set off the alarms, but these were ignored as false, and the theft remained undiscovered until 8:20 AM. On 21 January 2006 the Saliera was recovered by the Austrian police and is supposed to be returned to the Kunsthistorisches Museum in the coming days. One of the most important works by Cellini from late in his career was a life-size nude crucifix carved from marble. Although originally intended to be placed over his tomb, this crucifix was sold to the Medici family who gave it to Spain. Today the crucifix is in the Escorial Monastery near Madrid, where it has usually been displayed in an altered form — the monastery added a loincloth and a crown of thorns. Cellini, while employed at the papal mint at Rome during the papacy of Clement VII and later of Paul III, created the dies of several coins and medals, some of which still survive at this now defunct mint. He was also in the service of Alessandro de Medici, first duke of Florence, for whom he made in 1535 a forty-soldi piece with a bust of the duke on one side and standing figures of the saints Cosima and Damian on the other. Some connoisseurs attribute to his hand several plaques, "Jupiter crushing the Giants", "Fight between Perseus and Phineus", a Dog, etc. Other works are not directly attributed to him but are instead attributed to his workshop.

The important works which have perished include the uncompleted chalice intended for Clement VII; a gold cover for a prayer book as a gift from Pope Paul III to Charles V, Holy Roman Emperor – both described at length in his autobiography; large silver statues of Jupiter, Vulcan and Mars, wrought for Francis I during his sojourn in Paris; a bust of Julius Caesar; and a silver cup for the cardinal of Ferrara. The magnificent gold "button", or morse (a clasp for a cape), made by Cellini for the cape of Clement VII, the competition for which is so graphically described in his autobiography, appears to have been sacrificed by Pope Pius VI, with many other priceless specimens of the goldsmith's art, in furnishing the 30,000,000 francs demanded by Napoleon I at the conclusion of the campaign against the Papal States in 1797. According to the terms of the treaty, the pope was permitted to pay a third of that sum in plate and jewels. Fortunately there are in the print room of the British Museum three watercolour drawings of this splendid morse by F. Bertoli, done at the instance of an Englishman named Talman in the first half of the 18th century. The obverse and reverse, as well as the rim, are drawn full size, and moreover the morse with the precious stones set therein, including a diamond then considered the second largest in the world, is fully described. Benvenuto's works are mentioned as "priceless" in Mark Twain's The Prince and the Pauper.