The 1924–25 season was the 27th in the history of the Southern League. As in the previous season, the league was split into Eastern and Western Divisions.[1] Southampton II won the Eastern Division and Swansea Town II won the Western Division. Southampton were declared Southern League champions after defeating Swansea 2–1 in a championship play-off.
Mid Rhondda United, who finished fifth in the Western Division, were the only club to apply to join the Football League, but were unsuccessful in the vote.[2] Seven clubs left the league at the end of the season.
| Competition: | Southern Football League Eastern Division |
| Season: | 1924–25 |
| Winners: | Southampton II (1 title) |
| Promoted: | none |
| Relegated: | Northampton Town II (resigned) |
| Matches: | 272 |
| Total Goals: | 915 |
| Prevseason: | 1923–24 |
| Nextseason: | 1925–26 |
A total of 16 teams contest the division, including 15 sides from previous season and one new team.
Newly elected teams:
| Competition: | Southern Football League Western Division |
| Season: | 1924–25 |
| Winners: | Swansea Town II |
| Promoted: | none |
| Relegated: | Swansea Town II (resigned) Bridgend Town (resigned) Cardiff City II (resigned) Newport County II (resigned) Llanelly (resigned) Aberaman Athletic (resigned) |
| Matches: | 380 |
| Total Goals: | 1169 |
| Prevseason: | 1923–24 |
| Nextseason: | 1925–26 |
A total of 20 teams contest the division, including 18 sides from previous season and two new teams.
Newly elected teams:
Mid-Rhondda United were the only non-League club to enter the elections for a place in the Football League Third Division South. However, they received no votes and both League clubs were re-elected.
| Club | League | Votes | |
|---|---|---|---|
| Brentford | Football League Third Division South | 44 | |
| Merthyr Town | Football League Third Division South | 44 | |
| Mid-Rhondda United | Southern League | 0 |