The 1921–22 season was the 24th in the history of the Southern League. As in the previous season, the league was split into two sections, one for English clubs and one for Welsh clubs.[1] Plymouth Argyle reserves won the English section, whilst Ebbw Vale won the Welsh section. Plymouth Argyle reserves were declared champions after defeating Ebbw Vale 3-0 in a championship play-off. Pontypridd and Bath City were the only two Southern League clubs to apply for election to the Football League, though neither was successful.[2]
At the end of the season Gillingham reserves and Charlton Athletic reserves both left the league.
| Competition: | Southern Football League English Section |
| Season: | 1921–22 |
| Winners: | Plymouth Argyle II (1st title) |
| Promoted: | none |
| Relegated: | Gillingham II (resigned) Charlton Athletic II (resigned) |
| Matches: | 342 |
| Total Goals: | 1083 |
| Prevseason: | 1920–21 |
| Nextseason: | 1922–23 |
A total of 19 teams contest the division, including ten sides from previous season and nine new teams, seven of which were reserve teams.
Newly elected teams:
| Competition: | Southern Football League Welsh Section |
| Season: | 1921–22 |
| Winners: | Ebbw Vale |
| Promoted: | none |
| Relegated: | none |
| Matches: | 72 |
| Total Goals: | 225 |
| Prevseason: | 1920–21 |
| Nextseason: | 1922–23 |
A total of 9 teams contest the division, including nine sides from previous season and one new team.
Newly elected teams:
In addition to the two clubs finishing bottom of Football League Third Division South, three non-League clubs joined the election process, of which two were from the Southern League. However, both League clubs were re-elected.
| Club | League | Votes | |
|---|---|---|---|
| Southend United | Football League Third Division South | 36 | |
| Exeter City | Football League Third Division South | 32 | |
| Pontypridd | Southern League | 21 | |
| Bath City | Southern League | 1 | |
| Llanelly | Welsh National League (South) | 0 |