Ugolino di Prete Ilario was an Italian painter and mosaicist born in Siena around 1330 and who died in 1404. His name is tied above all to the cathedral of Orvieto, where he worked on the decoration of some of its most prominent spaces.
In 1364 he executed some of the frescoes in the chapel of the Holy Corporal in that cathedral. Later, in 1378, he was employed alongside other artists to decorate the walls of the tribune and choir behind the high altar of the same church. He also supplied the designs for some of the mosaics on the outer facade, a task that combined pictorial invention with the execution in tesserae.
At least one pupil is known from his workshop, Cola Petruccioli, which suggests that his practice continued into the following generation. The surviving documentation on his work is limited, so his profile is reconstructed mainly from the Orvieto commissions, which remain the clearest evidence of his activity.