Renowned tourist destination of great seafaring tradition located on the north-west coast of the Argentario. It is an active commercial center, a fishing and a seaside resort that overlooks a bay dominated by the Spanish Fortress. With Porto Ercole is one of the two main towns that make up the municipality.
The town is located on the north-western side of the Argentario promontory, just over 40 km south-east of Grosseto, about 10 km south-west from Orbetello and about 12 from Porto Ercole. The northern coast of Porto Santo Stefano, is divided between Punta Lividonia to the northwest and the mouth of the Canale di Santa Liberata.
Proceeding from west to east, the coast is high and rocky between Punta Lividonia and Punta della Madonnetta, which borders the inhabited center to the west. The coastal stretch on which the town faces, presents a promenade along the city road. Continuing along that direction you will first meet the old port, a tourist berth, and after another stretch of promenade along the Porto del Valle, the departure point for ferries to the Isola del Giglio and Giannutri, to which the area reserved for fishing vessels and shipyards.
Beyond the area of the main port, the coast becomes again high and rocky, along which the peninsula of Punta Nera and Calvello meet, where originally a coastal tower was found.
Porto Santo Stefano, located in the northern part of Monte Argentario, is the major center of this promontory. Due to its favorable geographical position it was frequented by the ancient peoples who sailed in the Mediterranean. The Romans have left noticeable traces of their presence, including the remains of the baths of Domitian and in their cards indicated the locality with various names, such as Portus Traianus and Portus ad Cetarias. Under the domination of the Sienese that goes from the beginning of the fifteenth to the middle of the sixteenth century the place becomes a landing of little importance subject to frequent raids by pirates. In this period the Argentiera tower was built in 1442, and some coastal towers. The development of the center began around 1550 under the Spanish governorship of Núñez Orejón de Ávila, and continued after the creation of the state of the Presidia and the construction of the Spanish fortress.
Porto S.Stefano in the early 1900s.
In 1646 Porto Santo Stefano was conquered by the French and then returned under Spanish rule in the same year, in 1707 it passed under the Austrian government, along with the entire State of the Presidi, in 1737 it came under the control of the Bourbons and in this period recorded the first important demographic development with the influx of many families from Campania, from the Island of Elba, and from the Ligurian Riviera . In 1801 he joined the kingdom of Etruria and in 1815 under the Treaty of Vienna he passed under the Grand Duchy of Tuscany. In 1842 the Grand Duke Leopold II of Lorena established the community of Monte Argentario, where Porto Santo Stefano represented the capital and Porto Ercole the fraction. In 1860, together with all of Tuscany, it became part of the Kingdom of Italy, a historic event was the stop of Garibaldi and the Thousand on May 9, 1860 during the transfer journey from Quarto to Marsala.
During the last world war, Porto Santo Stefano was a very important logistic base for the Germans, for this reason it was the scene of violent bombardments, the inhabited center was severely hit by the allies suffering the loss of many civilians. The episode was emphasized by Radio London,   as the success of the next winners of the conflict on the area that at the time constituted the true stronghold of the Wehrmacht in Italy.  The bombings made Monte Argentario the second most devastated Italian municipality, after Cassino .
The economy of Porto Santo Stefano, is essentially based on tourism activities, very developed along the coast and linked to the normal seasonality of Italian holidays. In addition to normal hotel and restaurant activities, there are those deriving from connections with the nearby Isola del Giglio and Giannutri Island. Since 2016, the location is the official port of call of the US shipping company Oceania Cruises , which deals with luxury cruises . Porto Santo Stefano has been boasting for several years the Blue Flag, a recognition given by the FEE to the best European seaside resorts  and the green flag for the best beaches for children .