Porto were the defending champions, after beating Arsenal 1–0 in the previous season's final, but were eliminated in the group stage.

The group winners, and two best runners-up, progressed into the knockout phase of the tournament.

[1] All matches - including fixtures between non-English teams - were played in England and Wales.

Athletic Bilbao, Benfica, Everton, Leicester City, PSV Eindhoven, Porto and Villarreal made their fifth appearance in the competition.

Brighton & Hove Albion, Paris Saint-Germain and Southampton made their debuts.