The 2002–03 Southern Football League season was the 100th in the history of the league, an English football competition.
Tamworth won the Premier Division and earned promotion to the Football Conference for the first time. Halesowen Town, Hastings United, Ilkeston Town and Folkestone Invicta were relegated from the Premier Division, whilst Dorchester Town, Merthyr Tydfil, Eastbourne Borough and Weston-super-Mare were promoted from the Eastern and Western Divisions, the former two as champions. Spalding United, St Leonards, Rocester and Racing Club Warwick were all relegated to the eighth level.
The Premier Division consisted of 22 clubs, including 17 clubs from the previous season and five new clubs:
| Competition: | Southern Football League Premier Division |
| Season: | 2002–03 |
| Winners: | Tamworth |
| Promoted: | Tamworth |
| Relegated: | Folkestone Invicta Halesowen Town Hastings United Ilkeston Town |
| Matches: | 462 |
| Total Goals: | 1257 |
| Prevseason: | 2001–02 |
| Nextseason: | 2003–04 |
The Eastern Division consisted of 22 clubs, including 18 clubs from the previous season and four new clubs:
| Competition: | Southern Football League Eastern Division |
| Season: | 2002–03 |
| Winners: | Dorchester Town |
| Promoted: | Dorchester Town Eastbourne Borough |
| Relegated: | Spalding United St. Leonards |
| Matches: | 462 |
| Total Goals: | 1497 |
| Prevseason: | 2001–02 |
| Nextseason: | 2003–04 |
The Western Division consisted of 22 clubs, including 18 clubs from the previous season and four new clubs:
| Competition: | Southern Football League Western Division |
| Season: | 2002–03 |
| Winners: | Merthyr Tydfil |
| Promoted: | Merthyr Tydfil Weston-super-Mare |
| Relegated: | Racing Club Warwick Rocester |
| Matches: | 462 |
| Total Goals: | 1382 |
| Prevseason: | 2001–02 |
| Nextseason: | 2003–04 |