Absence Makes the Heart Grow Fungus is the first instrumental and sixth overall studio album and by Omar Rodríguez-López, released by Infrasonic Sound on September 19, 2008. It is one of four solo albums completed in 2001 by Omar Rodríguez-López during the interim period following the demise of At the Drive-In and the formation of The Mars Volta. Absence... was tracked at Doug Messenger's North Hollywood studio only a few weeks after Rodriguez-Lopez recorded A Manual Dexterity: Soundtrack Volume One there, and is comparable to that project in both sound and atmosphere.

The album features several tracks that were "originally intended for use by The Mars Volta". The second half of "Hands Tied to the Roots of a Hemorrhage" was reworked as a middle section of "Eriatarka" on The Mars Volta's first full-length, De-loused in the Comatorium. "Tied Prom Digs on the Docks" features musical ideas that were later used on "Cassandra Gemini" on Frances the Mute. In addition, the song "Teflon" from the 2009 album Octahedron would be based on the instrumental "A Story Teeth Rotted For".

No personnel credits are listed in the insert for either the LP or CD, though it features a photograph of Jeremy Michael Ward never seen prior to this release.