papal residence in the Vatican north of St. Peter's Basilica. From the 4th century until the Avignonese period (1309–77) the customary residence of the popes was at the Lateran. Pope Symmachus built two episcopal residences in the Vatican, one on either side of the basilica, to be used for brief stays. Charlemagne built the Palatium Caroli on the north of St. Peter's to house his subjects during their visits to Rome. Other buildings added by Leo III and Eugenius III were modernized by Innocent III, who gave them added protection when he built a second fortified wall within that of Leo IV. Nicholas III began the first of the many buildings known today as papal palaces.

In the Renaissance Nicholas V rebuilt the north and west walls of the palace of Nicholas III and founded the Vatican Library (see Vatican Apostolic Library), making use of such architects as Leon Battista Alberti and Bernardo Rossellino. He also commissioned Fra Angelico to paint the stories of St. Stephen and St. Lawrence in the Chapel of Nicholas V.

Under commission from Sixtus IV, Giovanni dei Dolci built the Sistine Chapel. He also remodelled and decorated the Vatican Library. The rooms remodelled by Alexander VI are called the Borgia Apartments. Under Julius II, Bramante completed the north facade, two of the so-called logge (to which Raphael added a third). Raphael was commissioned to decorate the rooms of the Segnatura and of Heliodorus as well as the loggia overlooking the Courtyard of the Maresciallo.

Among the things built for Paul III were the Sala Regia and the Pauline Chapel, both designed by Antonio da Sangallo the Younger. The painters Giorgio Vasari, Taddeo Zucaro, and Daniele da Volterra decorated the Sala Regia; Michelangelo painted the martyrdom of St. Peter and the conversion of St. Paul in the Pauline Chapel (1542–50). The Casino of Pius IV was the work of Pirro Ligorio and Giovanni Salustio Peruzzi; today this building is the seat of the Pontifical Academy of Sciences. The three chapels of St. Stephen, of St. Peter, and of St. Michael, with paintings by Vasari and with stuccoes by Guglielmo della Porta, and the chapel of the Swiss Guards, painted by Giulio Mazzoni and Daniele da Volterra, date from the time of Pius V. Gregory XIII (1572–85) was responsible for the wing closing the north side of the present Courtyard of S. Damaso, containing rooms decorated by Antonio Tempestà and Mathys Bril and for the famous Gallery of Maps, designed by Ottaviano Mascherino, with maps of the regions of Italy from designs by Ignazio Danti. The present apartments along the eastern side of the Courtyard of S. Damaso were built in the time of Sixtus V by Domenico Fontana, who also made a new wing for the Vatican Library including the Sala Sistina, thereby cutting the Belvedere Courtyard in half.

In the Baroque period Urban VIII built the Hall of the Countess Matilda, today called the Matilda Chapel, which was decorated by Pietro da Cortona. Under Alexander VII, Bernini built the Scala Regia. In the late 18th and 19th centuries many of the additions and alterations had to do with the development of the Vatican Museum.