The 2017–18 FC Copenhagen season was F.C. Copenhagen's 26th season of existence, competing each year in the Danish Superliga, the top tier of football in Denmark. Outside of the Superliga, Copenhagen competed in the Danish Cup and the UEFA Champions League qualifying rounds.
F.C. Copenhagen had its worst season since the 1999-2000 campaign, finishing fourth in the 2017-18 Danish Superliga and being eliminated in the fourth round of the 2017-18 Danish Cup.
The Lions fared better in the 2017-18 UEFA Champions League, advancing to the playoff round by defeating MŠK Žilina in the second qualifying round and FK Vardar in the third qualifying round, before seeing their Champions League season end with a loss to Qarabağ FK.
The playoff loss qualified the team for the 2017-18 UEFA Europa League Group Stage. Copenhagen finished second in Group F and qualified for the round of 32, where Atlético Madrid prevailed, 5–1.