The Forgotten Arm is an album by singer-songwriter Aimee Mann with illustrations by Owen Smith. It was released in 2005 by Superego Records.

It is a concept album, telling the story of two characters who run off with each other to escape their problems, but end up in more trouble than either of them could have imagined.

The album reflects Mann's own boxing in its story and illustrations. The title is derived from a move in which one arm is used to hit the opponent, causing him to "forget" about the other arm, which is then used to deliver a harsher blow.

The album won the 2006 Grammy Award for Best Recording Package for Mann and Gail Marowitz (art directors).