Octahedron is the fifth full-length studio album by American progressive rock band the Mars Volta, released on June 23, 2009. The album was released by Warner Bros. Records in North America and Mercury Records worldwide. It is the last studio album to feature drummer Thomas Pridgen and guitarist John Frusciante, and the first not to feature contributions from keyboardist Isaiah "Ikey" Owens and multi-instrumentalist Adrián Terrazas-González.

Regarding the release, vocalist Cedric Bixler-Zavala states that the band "wanted to make the opposite of all the records we've done. All along we've threatened people that we'd make a pop record, and now we have."

It debuted at number 12 on the Billboard 200 albums chart with sales of 29,980 in its first week of release. As of March 2012, it has sold 84,000 copies in United States.