The 1919–20 season was the 22nd in the history of the Southern League, and the first following World War I. Portsmouth won the Southern League championship for the second time, whilst Mid Rhondda won Division Two.
The league was split into two national sections for England and Wales, with the winners of each section contesting a playoff for the Southern League championship.
The remaining clubs in Division Two moved to the Welsh Section.
[1] They were successful and, along with Leeds United, replaced Grimsby Town and Lincoln City in the Football League Second Division.
After the voting, 21 clubs remained in Southern League alongside Grimsby, having gained more votes than other non-elected clubs, were then elected into the newly created Third Division.