Ricardo de Burgos Bengoechea has been appointed for Milan-Celtic while Ruddy Buquet will referee AZ-Napoli and Fran Jovic will oversee Roma-Young Boys.
UEFA has appointed the referees for Europa League Matchday 5.
Milan host Celtic at the San Siro, the match kicks off at 5.55pm GMT on Thursday.
Napoli and Roma play at 8pm against AZ Alkmaar and Young Boys respectively.
Referee: Ricardo de Burgos Bengoechea (SPA)
Assistants:Inigo Prieto and Jon Nunez Fernandez
Fourth official: Adrian Cordero Vega
Referee: Ruddy Buquet (FRA)
Assistants: Guillaume Debart and Frederic Haquette
Fourth official:Jeremie Pignard quarto uomo.
Referee: Fran Jovic (CRO)
Assistants: Ivica Modric and Hrvoje Radic
Fourth official: Mario Zebec