Decasia is a 2002 American collage film by Bill Morrison, featuring an original score by Michael Gordon.

In 2013, Decasia was included in the annual selection of 25 motion pictures for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".

"[3] It begins and ends with scenes of a dervish and is bookended with old footage showing how film is processed.

Various films that were incorporated into Decasia have been positively identified: J. Farrell MacDonald's The Last Egyptian (1914), written, produced, and based on the novel by L. Frank Baum; William S. Hart's Truthful Tulliver (1917); Norman Dawn's A Tokyo Siren (1920); John H. Collins's The Man Who Could Not Sleep (1915); Eddie Lyons's Peace and Quiet (1921) and Phillips Smalley's The Mind Cure (1912).

[5] Decasia was included in the September 2014 box set release of Bill Morrison's collected works, from Icarus Films.