Napoli and Roma fans on their way to different matches clashed on the M1 motorway near the Tuscan city of Arezzo on Sunday.
The fighting broke out at around 1.30pm and involved about 200 people.
Both sets of fans threw flares, bottles and other objects at each other, causing part of the motorway to be shut for 50 minutes.
Some fans were seen using sticks and belts as weapons.
According to local media reports, a Rome fan was stabbed in the legs during the clash.
The Neapolitans were heading north to Genoa for their side’s Serie A match against Sampdoria, while the Roma fans were driving north to Milan for a game against Milan.