Ponti’s parents were Enrico Ponti and Giovanna Rigone. He did military service during World War I in the Pontonier Corps with the rank of captain, from 1916 to 1918, receiving the Bronze Medal and the Italian Military Cross. Gio Ponti graduated with a degree in Architecture in 1921 from the Politecnico di Milano University. Also in 1921, he married Giulia Vimercati; they eventually would have four children and eight grandchildren. Ponti began his architectural career in partnership with Mino Fiocchi and Emilio Lancia from 1923 through 1927, and then through 1933 with Lancia only, as Studio Ponti e Lancia PL. In these years he was influenced by and associated with the Milanese neo-classical Novecento Italiano movement. Output of the time includes the 1925 house on Via Randaccio in Milan, the 1926 Bouilhet villa in Garches, Paris, the 1929 Monument to the Fallen with the Novecento architect Giovanni Muzio, the Casa Rasini apartment blocks in Milan, and the 1930 Domus Julia–Domus Fausta complex on Via Letizia. Around 1933, Gio Ponti ended his relationship with Lancia and teamed with two engineers, Antonio Fornaroli and Eugenio Soncini, to form Studio Ponti-Fornaroli-Soncini which would last until 1945. Their first major commission was the 1936 company headquarters for the Italian chemical firm Montecatini, followed by a number of other industrial and university commissions through the war years, offices for Fiat, and the Palazzo del Liviano for the University of Padua in which Ponti himself painted frescos.

Gio Ponti in 1950 won the commission to design the 32-story Pirelli Tower in collaboration with Pier Luigi Nervi and Arturo Danusso. This was the second skyscraper built in Milan, and likely the climax of Ponti’s entire career. Construction began in 1956. In 1951, Ponti designed the master plan, and two individual block contributions, for the IINA l’Istituto Nazionale per le Assicurazione) Casa quarter housing project in Milan. In 1952 he went into partnership with the architect Alberto Rosselli (Studio Ponti-Fornaroli-Rosselli, P.F.R.: 1952–1976); after the death of Rosselli he continued to work with his longtime partner Antonio Fornaroli. From 1953 to 1957, he built the Hotel della Città et de la Ville and the Centro Studi Fondazione Livio e Maria Garzanti, in Forlì (Italy), by the assignment of Aldo Garzanti, a famous Italian publisher. As the Pirelli Tower attracted more attention, international commissions came in to Ponti’s office, for Caracas, Venezuela, ( Villa Planchart), Baghdad, Hong Kong, Eindhoven and the 1971 Denver Art Museum, and finally a series of Milanese churches: San Francesco in 1963, the church at Ospedale San Carlo in 1967, and the Taranto Cathedral in 1971. Between 1960 and 1962 Ponti designed and realize the first Italian Hotel Design: the Parco dei Principi (Sorrento).