He was born in Bergamo in 1908. After an apprenticeship with some artisans, he stayed for a short period in 1929 in Paris and then settled in Milan where he met Sassu and Birolli, who were part of the "Corrente" group with him. His first works in bronze, flanked by drawing, engraving, illustration and painting, are influenced by the then widespread "primitivism" and the influence of Medardo Rosso.
Back in Paris, struck by the impressionist lesson, he abandoned the rigid archaic schemes to advance in the development of an ever greater luministic sensitivity with a deep attention to plastic softness.
Between 1938 and 1939 the series of Cardinals begins,hieratic images in bronze, with a schematic pyramidal structure, then followed by the cycle of bronze bas-reliefs with the Depositions and the Crucifixions (1939-1942), themes then resumed after the war and reunited under the overall title of Christ in our humanity, which arose from the reaction to the violence of war.
In 1941 he obtained the chair of sculpture at the Brera Academy.
Between 1952 and 1964 he created the famous Porta della Morte for St. Peter's Basilica in Rome: the preparatory drawings, the numerous sketches and the door itself together constitute a rich synthesis of all the inspiring elements of his work and one of the major artistic complexes of contemporary art.
Among the other themes of the copious production of Manzù the portrait-busts (among which those of Inge, companion and inspirer of numerous works) to the nudes of girls and adolescents sitting on the chair or in the act of dancing, to inventions more or less openly erotic like the reliefs and drawings depicting the Artist with the model.
He died in Ardea in 1991.