1974–75 Isthmian League

The 1974–75 season was the 60th in the history of the Isthmian League, an English football competition.

Wycombe Wanderers won Division One, while Staines Town won Division Two.

Division One
Division One featured 22 clubs, including 20 clubs from the previous season and two clubs, promoted from Division Two:
 * Dagenham
 * Slough Town

Division Two
Division Two expanded up to 18 clubs, including fourteen clubs from the previous season and four new clubs:
 * Two clubs relegated from Division One:
 * Corinthian-Casuals
 * St Albans City


 * Two clubs switched from the Athenian League:
 * Boreham Wood
 * Croydon