The fight reportedly left another man in a coma, the Foreign Office said.
Reports in Italy say that the 21-year-old man was arrested on Thursday night after a fight outside the Bounty pub in Bologna, 75 miles (120km) from the enclave republic where England's World Cup qualifying match takes place.
Local newspaper La Repubblica reported that a 65-year-old England fan was in a coma in hospital after having major surgery on a head injury.
A Foreign office spokeswoman said: "We can confirm the arrest of a British national in Italy on 21 March. We are providing consular assistance."
La Repubblica reported that a group of at least seven football fans, who had been drinking, started fighting outside the pub in the Via delle Moline. They described the 65-year-old defending himself with a bar stool before being punched and then hitting his head on the ground as he fell.
England take on the part-time minnows of San Marino at the Stadio Olimpico, before Tuesday's crucial trip to Montenegro.