The first historical mention of the city as a Roman castrum whose foundations were laid on the site of today’s historic Old Town dates back to the 2nd century BC. In the 1st century Emperor Augustus granted Poreč city status and named it Coloniom Iuliom Parentium.
The turbulent history of this region saw many different rulers and each of them left their own imprint on the city. When the city was under Byzantine rule, bishop Euphrasius renovated the basilica. He took as a model the basilica in Ravenna whose golden mosaics were considered to be modern in that age. Bishops Euphrasius, St Maurus and St Eleuterius, whose figures are depicted in the basilica, have been protecting the city up to the present. Istria, and therefore also Poreč, were ruled by the Franks. In 1267 Poreč was ruled by Venice and it became the first Istrian city that chose to become part of the Republic of St Marco.
During the war between Venice and Genoa the city was plundered by Paganino Doria, a Genoese admiral who took away the relics of Poreč’s martyrs. Throughout history Poreč was known as the city of merchants and artisans. Its population was decimated by the plague that raged in the city. In 1667 it was populated by people exiled from Crete. In 1797 Napoleon marched through the city of St Maurus. After the fall of Napoleon Poreč became part of the Margravate of Istria under the jurisdiction of Austria. The Tsar’s patent of 1861 granted Istria autonomy and Poreč became the seat of the regional Parliament. At the beginning of the 20th century the famous Parenzana, a narrow gauge railway line, was built and it connected Poreč to Trieste. This opened the way for the growth of tourism and prosperity, the construction of first summerhouses and hotels. During the World War II the city suffered severe damage due to heavy bombardment.