The 1908–09 season was the 15th in the history of Southern Football League. Northampton Town won Division One and Croydon Common finished top of Division Two.[1] No clubs applied for election to the Football League.
| Competition: | Southern Football League Division One |
| Season: | 1908–09 |
| Winners: | Northampton Town (1st title) |
| Promoted: | none |
| Relegated: | none |
| Matches: | 420 |
| Total Goals: | 1276 |
| Prevseason: | 1907–08 |
| Nextseason: | 1909–10 |
A total of 21 teams contested the division, including 18 sides from previous season and three new teams.
Team promoted from 1907–08 Division Two:
Newly elected teams:
| Competition: | Southern Football League Division Two |
| Season: | 1908–09 |
| Winners: | Croydon Common |
| Promoted: | Croydon Common |
| Relegated: | Depot Battalion RE (resigned) 2nd Grenadier Guards (resigned) |
| Matches: | 42 |
| Total Goals: | 214 |
| Prevseason: | 1907–08 |
| Nextseason: | 1909–10 |
A total of seven teams contested the division, including three sides from the previous season and four newly elected teams.
Newly elected teams: