Giovanni Balducci, called Il Cosci after his maternal uncle, was an Italian mannerist painter.
He was born in Florence, he was trained by Giovanni Battista Naldini. He worked under the guidance and supervision of Vasari and under and with Federico Zuccari, on the massive, yet generally uninspired, fresco of the Final Judgment (1575–1579), on the inside of the Brunelleschi dome of the Duomo in Florence. He also frescoed a Last Supper in the church. These paintings, in addition to other transient ornamented arches and banners, were part of decorations developed to celebrate the wedding of Ferdinand I de' Medici, Grand Duke of Tuscany to Christina of Lorraine. During this time, Balducci also painted an altarpiece of the Mystical Marriage of St Catherine for the church of Sant'Agostino in San Gimignano.
From 1577-1580, he aided Naldini in the fresco decoration of the Altoviti Chapel in the church of Trinità dei Monti in Rome. He returned to Florence, to assist Alessandro Allori in the also uninspired decoration of Vasari's Gallery for the Uffizi. Under the patronage of Cardinal Alessandro de' Medici, who later became the short-lived Pope Leo XI, Balducci was engaged from 1588-1590, in painting a cycle of frescoes depicting scenes from the Life of Christ for the Oratorio di Gesù Pellegrino, located in Via San Gallo of Florence. From 1590-1591, he worked with Naldini in the decoration of Volterra Cathedral, painting in the Serguidi chapel a Miracle of Loaves and Fish.
By 1600, Balducci had moved to Naples where he painted altarpieces of St Dominic dispense the Rosary and St Peter Martyr for the church of Santa Maria della Sanità. He painted the Pardon of Carlo Gesualdo (1609) now in the church of Santa Maria delle Grazie in Gesualdo in the province of Avellino. He painted a number of frescoes in the cloister of Santa Maria del Carmine. He also frescoed ceilings for the church of the Annunziata in Maddaloni in Campania. He died in Naples.