Daniele Sciusco, 29, from Rome, admitted violent disorder ahead of the Anfield match on April 24.
On Friday, Preston Crown Court heard Irish Liverpool fan Sean Cox, 53, was still in a serious condition after suffering a head injury in the violence – although Sciusco was not directly involved in causing his injuries.
The court was told Sciusco was part of a group of Roma “ultras” who had flown from Italy for the match.
Video footage showed the group of about 25 fans, all dressed in dark clothing, going on to Walton Breck Road, outside the stadium just before kick-off.
Keith Sutton, prosecuting, said Sciusco had a belt in his hand as the group confronted Liverpool fans.
Mr Cox, from Dunboyne, Co Meath, was seen lying in the road after being attacked, as fighting continued around him.
Sentencing, Recorder of Preston Judge Mark Brown said: “The Champions League semi-final was a major international football event that was being televised across Europe, and your actions and the actions of the Italian group tarnished significantly what was intended to be a sporting and enjoyable occasion.
“It’s important to stress you are not being sentenced for the dreadful attack on Mr Cox, but it did occur during violent disorder of which you were a part, and the impact on him has been catastrophic.”
Another fan, Filippo Lombardi, 21, denies violent disorder and wounding/inflicting grievous bodily harm on Mr Cox and is due to stand trial later this year.