The 1999–2000 Sussex County Football League season was the 75th in the history of Sussex County Football League a football competition in England.[1] [2]
| Competition: | Sussex County Football League Division One |
| Season: | 1999–2000 |
| Winners: | Langney Sports |
| Relegated: | Shoreham |
| Matches: | 380 |
| Total Goals: | 1311 |
| Prevseason: | 1998–99 |
| Nextseason: | 2000–01 |
Division One featured 18 clubs which competed in the division last season, along with two new clubs, promoted from Division Two:
| Competition: | Sussex County Football League Division Two |
| Season: | 1999–2000 |
| Winners: | Sidlesham |
| Promoted: | Sidlesham Arundel Lancing |
| Matches: | 306 |
| Total Goals: | 1050 |
| Prevseason: | 1998–99 |
| Nextseason: | 2000–01 |
Division Two featured 14 clubs which competed in the division last season, along with four new clubs.
Also, Crawley Down Village changed name to Crawley Down.
| Competition: | Sussex County Football League Division Three |
| Season: | 1999–2000 |
| Winners: | Bosham |
| Promoted: | Bosham Wealden Crowborough Athletic |
| Matches: | 240 |
| Total Goals: | 920 |
| Prevseason: | 1998–99 |
| Nextseason: | 2000–01 |
Division Three featured twelve clubs which competed in the division last season, along with four new clubs:
Also, St Francis Hospital changed name St Francis.