The referee for the Athletic Club vs Arsenal UCL Matchday 1 clash on September 16, 2025 has been announced as Donatas Rumsas. The 37-year-old Lithuanian is the same ref who was in charge of Manchester United’s European defeats to FC Copenhagen (4-3 loss in the 23/24 Champions League) and FC Astana (2-1 loss in the 19/20 Europa League).
In that 4-3 Man Utd defeat to FCK, Rumsas also sent off Marcus Rashford and awarded penalties to both clubs, which were converted by Diogo Goncalves and Bruno Fernandes respectively.
Interestingly, this is the first time Rumsas will also referee a game involving a La Liga club in the Champions League.

