| Continentalcup2: | New clubs in League |
| Continentalcup2 Qualifiers: | 23 (see tables) |
| Nextseason: | 1921–22 |
The 1920–21 season was the 29th season of The Football League.
The Football League Third Division was introduced, in effect the Third Division South of the following season, when Third Division North was introduced. This expanded the League's operational radius all the way to the south coast of England, as the number of member clubs increased from 44 to 66.
The new Third Division was formed by clubs of the Southern Football League Division One of the previous season, except for Cardiff City. Cardiff City became the first Welsh club to enter the League, and since they were the strongest club in Wales in the era, they were invited directly into the Second Division. Grimsby Town took its place in the new Third Division, thereby being the first club relegated to the League's third tier. Leeds United were also elected into the Second Division to replace Leeds City after its debacle. Lincoln City were not re-elected to the Second Division and thus Port Vale's Second Division place was formalized as well.
Beginning in the 1894–95 season, clubs finishing level on points were separated according to goal average (goals scored divided by goals conceded). In case one or more teams had the same goal difference, this system favoured those teams who had scored fewer goals. The goal average system was eventually scrapped beginning with the 1976–77 season.
During the first six seasons of the league, (up to the 1893–94 season), re-election process concerned the clubs which finished in the bottom four of the league. From the 1894–95 season and until the 1920–21 season the re-election process was required of the clubs which finished in the bottom three of the league.
| Competition: | First Division |
| Season: | 1920–21 |
| Winners: | Burnley 1st English title |
| Relegated: | Derby County Bradford Park Avenue |
| League Topscorer: | Joe Smith (38 goals)[1] |
| Biggest Home Win: | (25 September 1920) (27 November 1920) (25 December 1920) (5 February 1921) |
| Biggest Away Win: | (16 October 1920) (20 November 1920) (12 February 1921) (26 March 1921) |
| Highest Scoring: | (1 January 1921) |
| Matches: | 462 |
| Total Goals: | 1276 |
| Prevseason: | 1919–20 |
| Nextseason: | 1921–22 |
| Competition: | Football League Second Division |
| Season: | 1920–21 |
| Winners: | Birmingham (2nd title) |
| League Topscorer: | Sydney (Syd) Puddefoot (West Ham United), 29 |
| Biggest Home Win: | West Ham United – Coventry City 7–0 (1 Jan 1921) |
| Biggest Away Win: | Rotherham County – Bury 0–5 (11 Dec 1921) |
| Highest Scoring: | Rotherham County – South Shields 5–4 (2 Oct 1920) |
| Matches: | 462 |
| Total Goals: | 1061 |
| Nextseason: | 1921–22 |
| Competition: | Football League Third Division |
| Season: | 1920–21 |
| Winners: | Crystal Palace (1st title) |
| League Topscorer: | John Conner (Crystal Palace), 28 Ernie Simms (Luton Town), 28 George Whitworth (Northampton Town), 28 |
| Continentalcup2: | Failed re-election |
| Continentalcup2 Qualifiers: | None |
| Matches: | 462 |
| Total Goals: | 1133 |
| Nextseason: | 1921–22 |