The 2005 American Le Mans Series season was the 35th season for the IMSA GT Championship, with it being the seventh under the American Le Mans Series moniker. It was a series for Le Mans Prototypes (LMP) and Grand Touring (GT) race cars divided into 4 classes: LMP1, LMP2, GT1, and GT2. It began March 19, 2005 and ended October 16, 2005 after 10 races.