The 2004 Le Mans Endurance Series was the inaugural season of ACO's Le Mans Endurance Series. It is a series for Le Mans prototype and Grand Touring style cars broken into 4 classes: LMP1, LMP2, GTS, and GT. It began on 9 May 2004 and ended on 13 November 2004 after 4 rounds.
This season was preceded by the 1000km of Le Mans held in 2003 as a development race for the creation of the LMES.