The 1921 Norwegian Football Cup was the 20th season of the Norwegian annual knockout football tournament. The tournament was open for all members of NFF. This was the third consecutive year that Frigg played in the final, but after having lost the previous two they won 2–0 against Odd in this year's final and won their third title. Ørn were the defending champions, but were eliminated by Brann in the quarterfinal.
Qualifying round
|colspan="3" style="background-color:#97DEFF"|Replay
First round
|colspan="3" style="background-color:#97DEFF"|Replay
Second round
|colspan="3" style="background-color:#97DEFF"|Replay
Third round
Quarter-finals
Semi-finals
|colspan="3" style="background-color:#97DEFF"|Replay
Final
Frigg: Gustav Magnussen Birger Eriksen Yngvar Tørnros Georg Deans Ellef Mohn Fritz Semb Thorstvedt Einar Hansen Hans Dahl Gelland Nilsen Rolf Semb Thorstvedt Trygve SmithOdd: GK Ingolf PedersenDF Thaulow GobergDF Peder HenriksenMF UnknownMF UnknownMF UnknownFW Nils ThorstensenFW Haakon HaakonsenFW Bertel UlrichsenFW Einar Gundersen FW Unknown
See also 1921 in Norwegian football
References