Viktor Kassai

Kassai was preselected as a referee for the 2010 FIFA World Cup.[3] He refereed in the first leg of the AFC 5th vs OFC winner qualifier between Bahrain and New Zealand.

On 5 July, it was announced that he would be in charge for the Germany vs Spain semifinal. It was his fourth match in the World Cup. This is the highest prestige match a Hungarian referee has been in charge of since Sándor Puhl's 1994 FIFA World Cup Final.

His first appearance in the 2010 FIFA World Cup was a group stage match between Brazil and North Korea on 15 June 2010, which Brazil won 2–1. He refereed two matches in the group stage. The United States vs Ghana match finished after extra time, becoming the first match in the World Cup to happen so. It was the first time that either Ghana or the United States played in a World Cup match ending in extra time.

Kassai was the head of an all-Hungarian crew in the 2011 UEFA Champions League Final at Wembley Stadium in London, where he cautioned two players apiece on both the Barcelona (Daniel Alves and Victor Valdés) and Manchester United (Antonio Valencia and Michael Carrick) sides.

At the UEFA Euro 2012, Kassai officiated matches Spain vs Italy and England vs Ukraine. This was the first international tournament where two additional assistant referees were introduced on the goal-lines.[4] During the England and Ukraine game a Ukrainian strike was hooked away by an English defender, but TV re-plays showed that the ball had crossed the line.[5] This introduced a debate on the effectiveness of the inclusion of the two additional officials and the need for goal-line technology.[5] FIFA president Sepp Blatter said, "goal-line technology was a necessity" following the England vs Ukraine match.[6]

On 14 December 2016, Kassai became the first referee to award a penalty after viewing a video replay.[7]

On 9 January 2020 he was appointed the head of refereeing department of the Russian Football Union.[8]