The Hours of Giangaleazzo Visconti is a Roman-liturgy illuminated book of the Hours, produced in two volumes in Milan for Gian Galeazzo Visconti. It was begun in 1388 by Giovannino de' Grassi and completed around 1428 by Belbello da Pavia during the reign of Gian's son Filippo Maria Visconti.
It is now in the Biblioteca Nazionale in Florence.