The 1999–2000 Sussex County Football League season was the 75th in the history of Sussex County Football League a football competition in England.
[1][2] Division One featured 18 clubs which competed in the division last season, along with two new clubs, promoted from Division Two: Division Two featured 14 clubs which competed in the division last season, along with four new clubs.
Also, Crawley Down Village changed name to Crawley Down.
Division Three featured twelve clubs which competed in the division last season, along with four new clubs: Also, St Francis Hospital changed name St Francis.