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.

The schedule change from 2004 to 2005 was minimal, with only one event being added to the existing schedule. The Grand Prix of Atlanta returned once more, once again shortly after the 12 Hours of Sebring.

* Was on the entry list but did not participate in the event.

Overall winner in bold.

† - The #8 B-K Motorsports entry failed to finish but completed enough laps to score points.

Points are awarded to the top 10 finishers in the following order:

Exceptions were for the 4 Hour Monterey Sports Car Championships was scored in the following order:

And for the 12 Hours of Sebring and Petit Le Mans which award the top 10 finishers in the following order: