The 1930–31 season was the 33rd in the history of the Southern League.
The league consisted of Eastern and Western Divisions.
[1] Dartford won the Eastern Division on goal average (had goal difference been used, Aldershot Town would have been champions) and Exeter City reserves won the Western Division.
Dartford were declared Southern League champions after winning a championship play-off 7–2.
Team relegated from 1929–30 Football League: Two Southern League clubs, Aldershot and Merthyr Town, applied to join the Football League, with Merthyr applying to join both Division Three North and Division Three South.