Born on 30 May 1981 in Bern, Stephan Klossner is a professional in the field of biology research. He officiated his first top-flight league encounter on 15 August 2010, an away 2-1 victory of Grasshopper CZ over FC St.Gallen.

Since then he has been a regular referee in the Swiss league and got his FIFA badge in 2012, starting with Elite round encounters of the UEFA European Under-19 Championship. On that same season he handled his first UEFA Europa League qualifying matches and, in 2013, he took charge of his first group stage match in the competition and made his debut in the qualifying stage of the UEFA Champions League.

He has refereed three UEFA Europa League group stage matches in total. Among them, the 2-2 draw between Qarabağ FK and FC Slovan Liberec earlier this season, a game corresponding to PAOK’s UEL group.

The 35-year-old will be accompanied in “Artemio Franchi” by Remy Zgraggen and Marco Zürcher, the assistant referees, with Johannes Vogelacting as fourth official. Alain Bieri and Sascha Amhof complete the team as additional assistant referees.