Mirobriga was an ancient city in the westernmost part of Lusitania in Roman times. It was mentioned by Pliny the Elder and Ptolemy.

The city is generally associated with the archaeological site near the village of Santiago do Cacém. The Roman mines of Caveira, Mina de São Domingos and Aljustrel are each about a day's journey inland. The nearest Roman town was Cetóbriga (now Setúbal), 35 kilometres to the north.