The foot of gilt bronze fibula was discovered in 2005 during archaeological investigations of locality 85 in Sirmium, that is assumed to have been the remains of the imperial palace. Ornament on the foot enclosed within rectangular field is executed in the niello technique. End of the foot is bent at the right angle and the Christogram is engraved on it with Greek letters alpha and omega engraved above its side arm. The preserved part of fibula makes possible reconstruction of its appearance and attribution to the group of massive bronze crossbow fibulae, which were produced in the second half of the 4th century and characterized by decoration consisting of gilding, niello, Christogram motif and/or the busts of young men in medallions.