Born in Siena under the name of Fabio Chigi, he belonged to the famous family of Tuscan bankers; he was the great-grandson of Pope Paul V, and as was the case with the offspring of the nobility, he was educated at home by private tutors, who took care of theological and cultural formation. He then obtained a degree in philosophy, canon law and theology at the University of Siena. From an early age he showed strong religious and literary talents, and from many sources he was described as austere and zealous in the faith. In 1629 he was appointed pontifical vice-legate of Ferrara, a position he held until 1634, when he arrived in Malta as an Inquisitor. On 8 January 1635 he was elected bishop of Nardò: the consecration took place on 1 July of the same year. He remained in his diocese until 1639, the year of his nomination as Papal Nuncio of Cologne (1639-1651).
He did not take part in the negotiations that led to the Peace of Westphalia in 1648, not recognizing the exponents of the various religious movements that had formed, their official status. So he refused to deal with heretics, and protested when the concluding document was disclosed as it, by not resolving the doctrinal issues, had only put an end to the Thirty Years War and established a balance between the European powers.
He was created cardinal by Pope Innocent X in the consistory of February 19, 1652, and on March 12 of the same year he was given the cardinal title of Santa Maria del Popolo. On 13 May 1653 he was elected bishop of Imola. Pope Innocent X called Chigi back to Rome and later made him cardinal secretary of state.
On the death of Innocent X, being among other candidates favored by Spain, he was elected Pope after eighty days of conclave, on 7 April 1655. The electors gathered in the conclave believed that he was suitable for his many diplomatic and cultural qualities, but also for his lifestyle. In fact, he strongly opposed the rampant nepotism at that time.
From the first years of his pontificate, Alexander VII simply lived and forbade relatives even to visit him in Rome; but in the consistory of April 24, 1656, he announced that his brother and grandchildren would join him in Rome to assist him. The administration was widely placed in the hands of his relatives: he gave them the most remunerative civil and ecclesiastical offices, together with palaces and princely properties.
Alexander did not appreciate the affairs of state, preferring literature and philosophy; a collection of his poems in Latin appeared in Paris in 1656, with the title of Philomathi Labores Juveniles. He also encouraged the architecture and general improvement of Rome, where he demolished buildings to straighten and widen the streets and had the opportunity to be a great patron of Gian Lorenzo Bernini. He commissioned the decorations of the church of Santa Maria del Popolo, the churches of several Cardinals Chigi, the Scala Regia, the altar of the Chair in the Basilica of San Pietro, and in particular sponsored the construction of the magnificent Bernini colonnade in the square of the basilica Vatican. In 1661, when Ariccia passed from the Savelli's dominion to that of the Chigi family, Alessandro undertook an important restoration of the village, making use of the precious work of the same Bernini and his young assistant Carlo Fontana. Of particular interest are the restoration project of the palace and the creation of the Collegiate Church of Santa Maria Assunta.
During the pontificate of Alexander VII came the conversion of Queen Christina of Sweden who, after her abdication, went to live in Rome. It was the pope himself who conferred the baptism on Christmas Day 1655.
In foreign policy he had to juggle the struggles of autonomy of national states. Alexander's pontificate was overshadowed by the constant friction with Cardinal Giulio Mazzarino, adviser to Louis XIV of France, who opposed him during the negotiations that led to the Peace of Westphalia, and which defended the prerogatives of the Gallican Church. During the conclave Mazzarino had proved hostile to the election of Chigi, but was eventually forced to accept it as a compromise. However, it prevented Louis XIV of France from sending the usual embassy of obedience to Alexander VII and, until he was alive, prevented the appointment of a French ambassador to Rome, managing diplomatic affairs by cardinal protectors, usually personal enemies of the Pope In 1662 the Duke of Crequi was appointed ambassador. Because of the abuse of asylum rights, traditionally granted to the diplomatic districts of Rome, precipitated a dispute between France and the Papacy, with the consequence of the temporary loss of Avignon and the forced acceptance of the humiliating Treaty of Pisa, in 1664. Alexander favored the claims of the Spaniards against the Portuguese.
He also encouraged the Jesuits in all their businesses. When the Venetians asked Crete for help against the Ottomans, Alexander promised in return that the Jesuits could return to the Venetian territory, from which they were expelled in 1606. He also continued to support the Jesuits in their conflict with the Jansenists, the whose sentence he had supported as an advisor to Innocent X.
The French Jansenists argued that the sentences condemned in 1653 were not actually in Augustusus, written by Giansenio. Alexander VII confirmed that they were present, with the bull Ad Sanctam Beati Petri Sedem (October 16, 1656), declaring that the five propositions of Jansenio, mainly concerning the grace and nature of man, were heretical. The Pope also sent in France a form, which was to be signed by the whole clergy, as a means to identify and eradicate Jansenism, and which also found wide acceptance among public opinion.
In 1661, in order to prevent the circulation of unorthodox contents, he prohibited the translation of the Roman missal into French; in 1665 he canonized Francis de Sales, whose figure as a faithful servant of the Gospel and the poor had wide fame among his contemporaries.
Alexander died in 1667; his funeral monument was commissioned to Gian Lorenzo Bernini and can still be admired today in the Basilica of San Pietro; Pope Clement IX succeeded him.