Some scholars contend that the Molossus was a dog used by the Ancient Greeks for fighting. They describe it as having a wide, short muzzle and a heavy dewlap (similar to modern Mastiff breeds) that was used to fight tigers, lions, elephants, and men in battle. A Roman copy of a Greek original sculpture of a guard dog (known as the Jennings Dog) is generally considered to represent a Molossus and can be seen at the British Museum.
Most scholars agree the Molossus originated with the Molossis people in the mountainous regions of northwest Ancient Greece (modern Greece northwest and Southern Albania before the Common Era). The Molossians were renowned for their vicious hounds, which were used by Molossian shepherds of Epirus in the mountains of northwestern Greece to guard their flocks. The poet Grattius, a contemporary of Ovid, writes "...when serious work has come, when bravery must be shown, and the impetuous War-god calls in the utmost hazard, then you could not but admire the renowned Molossians so much."
The breed was a native to Greece and the rest of the Balkans, it later migrated to Italy and other places of the Greek World by Hellenic tribes who started to colonize in various regions of the world. Virgil says that in ancient Greece the heavier Molossian dogs were often used by the Greeks and Romans for hunting (canis venaticus) and to watch over the house and livestock (canis pastoralis). "Never, with them on guard," says Virgil, "need you fear for your stalls a midnight thief, or onslaught of wolves, or Iberian brigands at your back."Aristotle mentions them in the history of animals and praises their bravery and physical superiority.