The 1965–66 FA Cup was the 85th staging of the world's oldest football cup competition, the Football Association Challenge Cup, commonly known as the FA Cup. Everton won the competition for the third time, beating Sheffield Wednesday 3–2 in the final at Wembley.

Matches were scheduled to be played at the stadium of the team named first on the date specified for each round, which was always a Saturday. Some matches, however, might be rescheduled for other days if there were clashes with games for other competitions or the weather was inclement. If scores were level after 90 minutes had been played, a replay would take place at the stadium of the second-named team later the same week. If the replayed match was drawn further replays would be held until a winner was determined. If scores were level after 90 minutes had been played in a replay, a 30-minute period of extra time would be played.