The 1902–03 season was the ninth in the history of Southern League.
Southampton won Division One for the 5th time in seven seasons.
At the end of the season, test matches were held between the bottom two clubs in Division One and the top two clubs in Division Two.
Brentford beat Fulham 7-2 to retain their place in Division One, although Fulham were promoted anyway after Division One was expanded to 18 clubs.
[1] Brighton beat Watford 5-3 in the other match, which saw the two clubs swap divisions.