Giambattista Tiepolo was born on March 5, 1696 in Venice, the last of six children of sea-captain, Domenico Tiepolo and his wife, Orsetta. While the Tiepolo surname belongs to a patrician family, Giambattista's father did not claim noble lineage. The future artist was baptised in his parish church (S. Pietro di Castello) as Giovanni Battista, in honour of his godfather, a Venetian nobleman called Giovanni Battista Dorià. His father Domenico died a year after his birth, leaving Orsetta in difficult financial circumstances.
Giambattista was initially a pupil of Gregorio Lazzarini, but the influences from elder contemporaries such as Sebastiano Ricci and Giovanni Battista Piazzetta are stronger in his work. At 19 years of age, Tiepolo completed his first major commission, the Sacrifice of Isaac (now in the Accademia). He left Lazzarini studio in 1717, and was received into the Fraglia guild of painters.
In 1719, Tiepolo married Maria Cecilia Guardi, sister of two contemporary Venetian painters Francesco and Giovanni Antonio Guardi. Together, Tiepolo and his wife had nine children. Four daughters and three sons survived childhood. Two sons, Domenico and Lorenzo, painted with him as his assistants and achieved some independent recognition. His third son became a priest.
A patrician from the Friulan town of Udine, Dionisio Delfino, commissioned from the young Tiepolo the fresco decoration of the chapel and palace (1726-1728). It was an almost revolutionary accomplishment using novel pale tonalities and airy handling. Incorporating Sebastiano Ricci’s maniera paolesca, Tiepolo at once distanced himself from the chiaroscuro typical of the Baroque, but maintained the theatrical grandeur of Rubens. He is considered by many as prototype painter of the decorative Italian Rococo movement of the 18th century. Tiepolo's first masterpieces in Venice were a cycle of enormous canvases painted to decorate a large reception room of Ca' Dolfin, Venice (ca. 1726–1729), depicting ancient battles and triumph.
He was soon in high demand, which he matched with an astounding prolixity. He painted canvases for churches such as that of Verolanuova (1735-40), for the Scuola dei Carmini (1740-47), and the Scalzi 1743-44]]), a ceiling for the Palazzi Archinto and Casati-Dugnani in Milan (1731), the Colleoni Chapel in Bergamo (1732-33), a ceiling for the Gesuati (S.Maria del Rosario) in Venice of St. Dominic Instituting the Rosary (1737-39), Palazzo Clerici, Milan (1740), decorations for Villa Cordellini at Montecchio Maggiore (1743-44) and for the salon of the Palazzo Labia, now a television studio in Venice, showing the Story of Cleopatra (1745-50).
By 1750, Tiepolo's reputation was firmly established throughout Europe, and accompanied by his son Giandomenico, he traveled to Würzburg at the call of Prince Bishop Karl Philipp von Greiffenklau in 1750, where he resided for three years and executed magnificent ceiling paintings in the New Residenz palace. His painting for the grand staircase is the largest ceiling fresco in the world at 7287 square feet (677 m²), and was completed in collaboration with his sons, Giandomenico and Lorenzo. His Allegory of the Planets and Continents depicts Apollo, embarking on his daily course; deities around him symbolize the planets; allegorical figures (on the cornice) represent the four continents, notably including America.
He then returned to Venice in 1753, where he was elected President of the Academy of Padua. The fame of his works led to many requests for commissions: for example, theatrical frescoes for churches; the Triumph of Faith for the Chiesa della Pietà; panel frescos for Ca' Rezzonico (which now also holds his ceiling fresco from the Palazzo Barbarigo); and paintings for patrician villas in the Venetian countryside, such as Villa Valmarana (Vicenza) and a large panegyric ceiling for the now nearly vacant Villa Pisani in Stra.
In 1761, Charles III commissioned from the painter a large ceiling fresco to decorate the throne room of the royal palace of Madrid. The panegyric theme is the Apotheosis of Spain. In Spain, he incurred the jealousy and the bitter opposition of Anton Raphael Mengs. Tiepolo died in Madrid on March 27, 1770.
After his death, the rise of stern Neoclassicism and the post-revolutionary decline of royal absolutism led to the slow decline of the Tiepolo style, but had failed to dent his impact on artistic progress. By 1772 Tiepolo was sufficiently famous to be documented as painter to Doge Giovanni Cornaro, in charge of the decoration of Palazzo Mocenigo a San Polo.