| Competition: | safl |
| Year: | 1921 |
| Teams: | 8 |
| Count: | 9 |
| Mpcount: | 13 |
| Matches: | 61 |
| Highattend: | 34,000 (Grand Final, vs) |
| Top Goal Scorer: | Roy Bent (42 goals) |
| Magarey Medal: | John Karney (5 votes) Charlie Adams (5 votes) Dan Moriarty (5 votes) Wat Scott (5 votes) |
| Prevseason: | 1920 |
| Nextseason: | 1922 |
The 1921 South Australian Football League season was the 42nd season of the top-level Australian rules football competition in South Australia.
The competition expanded from seven to eight teams with being admitted to the seniors after one year in the B Grade (Reserves).[1]
The season opened on Saturday 7 May with the opening fixture between and, and concluded on Saturday 8 October with the Grand Final, in which Minor Premiers went on to record its 9th premiership, defeating by 8 points.
, also made the top (final) four teams and participated in the finals series.,,, all missed the top four. Glenelg finished winless (as they also did in next three seasons 1922–1924) to "win" the wooden spoon in its first season.[2]
See main article: 1921 SAFL Grand Final.