The 1890–91 FA Cup was the 20th edition of the world's oldest association football knockout competition, The Football Association Challenge Cup, or FA Cup.

Advancing from the qualifying rounds were Chester, Halliwell, Middlesbrough Ironopolis, Sunderland Albion, Sheffield United, Long Eaton Rangers, Lincoln City, Kidderminster, Crusaders (based in Leyton) and the team from the 93rd Highland Regiment, which was stationed in Aldershot at this time. Middlesbrough Ironopolis, Kidderminster and the 93rd Highland Regiment were featuring at this stage for the first time, with the Highlanders having gone on what is now considered the first giant-killing run through the FA Cup qualifying rounds. The military team defeated future Premier League members Luton Town (at Dunstable Road), Watford, Swindon Town and Ipswich Town (at Portman Road) to secure their place in the competition proper.

In order to bring the number of teams up to 32, a further 10 non-League clubs entered the competition in the first round proper. Stoke was exempted to this stage despite having been voted out of the Football League at that year's Annual General Meeting, while Clapton, Nottingham Forest, Darwen, Crewe Alexandra, Casuals, The Wednesday, Old Westminsters, Birmingham St George's and Royal Arsenal received byes.

For information on all matches played from the preliminary round to the fourth qualifying round, see 1890–91 FA Cup qualifying rounds.

• FA Cup Results Archive