The 2005–06 Spartan South Midlands Football League season is the 9th in the history of Spartan South Midlands Football League a football competition in England.
| Competition: | Spartan South Midlands Football League Premier Division |
| Season: | 2005–06 |
| Winners: | Oxford City |
| Promoted: | Oxford City Hillingdon Borough Hanwell Town |
| Relegated: | Harpenden Town |
| Matches: | 380 |
| Total Goals: | 1201 |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
The Premier Division featured 17 clubs which competed in the division last season, along with three new clubs:
Also, Haywood United changed name to Aylesbury Vale.
| Competition: | Spartan South Midlands Football League Division One |
| Season: | 2005–06 |
| Winners: | Colney Heath |
| Promoted: | Colney Heath |
| Matches: | 272 |
| Total Goals: | 1018 |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
Division One featured 14 clubs which competed in the division last season, along with three new clubs:
| Competition: | Spartan South Midlands Football League Division Two |
| Season: | 2005–06 |
| Winners: | Aston Clinton |
| Matches: | 306 |
| Total Goals: | 1290 |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
Division Two featured 15 clubs which competed in the division last season, along with three new clubs:
Also, Padbury B T F C changed name to Padbury United.