Polygonal masonry is a technique of stone construction of the ancient Mediterranean world. True polygonal masonry may be defined as a technique wherein the visible surfaces of the stones are dressed with straight sides or joints, giving the block the appearance of a polygon.
This technique is found throughout the Mediterranean and sometimes corresponds to the less technical category of Cyclopean masonry.
In Italy it is particularly indicative of the region of Latium, but it occurs also in Etruria, Lucania, Samnium, and Umbria; scholars including Giuseppe Lugli have carried out studies of the technique. Some notable sites that have fortification walls built in this technique include Norba, Signia, Alatri, Boiano, Circeo, Cosa, Alba Fucens, Palestrina, and Terracina.