The 1945–46 season was Birmingham City Football Club's first season played under that name in nationally-organised football. The club had been called Birmingham F.C. since 1905, and the City suffix was added in 1943. Although the Football League did not resume until the 1946–47 season, the FA Cup restarted in 1945. Birmingham reached the semi-final, in which they lost to Derby County after extra time in a replay, played at Maine Road, Manchester, in front of 80,407 spectators. In league competition, Birmingham were champions of the first and only edition of the Football League South, taking the title on goal average from local rivals Aston Villa.