The 1998–99 Sussex County Football League season was the 74th in the history of Sussex County Football League a football competition in England.[1] [2]
| Competition: | Sussex County Football League Division One |
| Season: | 1998–99 |
| Winners: | Burgess Hill Town |
| Relegated: | Hailsham Town Broadbridge Heath |
| Matches: | 380 |
| Total Goals: | 1221 |
| Prevseason: | 1997–98 |
| Nextseason: | 1999–2000 |
Division One featured 17 clubs which competed in the division last season, along with three new clubs, promoted from Division Two:
| Competition: | Sussex County Football League Division Two |
| Season: | 1998–99 |
| Winners: | Sidley United |
| Promoted: | Sidley United Three Bridges |
| Relegated: | Crowborough Athletic Newhaven |
| Matches: | 306 |
| Total Goals: | 989 |
| Prevseason: | 1997–98 |
| Nextseason: | 1999–2000 |
Division Two featured 13 clubs which competed in the division last season, along with five new clubs.
| Competition: | Sussex County Football League Division Three |
| Season: | 1998–99 |
| Winners: | Oving Social Club |
| Promoted: | Oving Social Club Westfield |
| Relegated: | Buxted Midhurst & Easebourne |
| Matches: | 240 |
| Total Goals: | 817 |
| Prevseason: | 1997–98 |
| Nextseason: | 1999–2000 |
Division Three featured 13 clubs which competed in the division last season, along with three new clubs: