The 1905–06 season was the 12th in the history of Southern League. Fulham won Division One and Crystal Palace finished top of Division Two. No clubs were relegated from Division One as it was expanded to 20 clubs the following season.[1] No clubs applied to join the Football League.
| Competition: | Southern Football League Division One |
| Season: | 1905–06 |
| Winners: | Fulham (1st title) |
| Promoted: | none |
| Relegated: | none |
| Matches: | 306 |
| Total Goals: | 812 |
| Prevseason: | 1904–05 |
| Nextseason: | 1906–07 |
A total of 18 teams contest the division, including 17 sides from previous season and one new team.
Newly elected team:
| Competition: | Southern Football League Division Two |
| Season: | 1905–06 |
| Winners: | Crystal Palace |
| Promoted: | Crystal Palace Leyton |
| Relegated: | Southern United (resigned) Watford II (resigned) Grays United (resigned) |
| Matches: | 156 |
| Total Goals: | 590 |
| Prevseason: | 1904–05 |
| Nextseason: | 1906–07 |
A total of 13 teams contest the division, including 9 sides from previous season and four new teams, all of them are newly elected teams.
Newly elected teams: