The son of a silversmith, the earlier part of his career was spent in his native Rome, where he trained under Giovanni Battista Maini and enjoyed some success, including a commission for the basilica of Saint Peter’s. His expertise in ancient sculpture led to his transfer to Florence in 1769, where he was named official court sculptor the following year and embarked on the restoration of major antiquities in the Medici collections, including the Niobe group. He also carved skilful copies of antique statues and busts, including the Venus de’ Medici in the National Galleries of Scotland. Spinazzi executed three important monuments to Florentine worthies in the church of Santa Croce, and a virtuoso veiled figure of Faith in Santa Maria Maddalena de’ Pazzi, which took inspiration from comparable figures by the Venetian sculptor Antonio Corradini. From 1784 until his death he was professor of sculpture at the Florentine Accademia delle Belle Arti.