Idée fixe may refer to:

• Idée fixe (psychology), a psychological disorder
• Idée Fixe (album), a 1978 album by Aerolit
• Dogmatix, the English name of an Asterix comics character, called Idéfix in French
• Idée fixe (music), a recurring theme or motif, as in the Symphonie fantastique by Hector Berlioz

• Fixation (disambiguation)
• Leitmotif, a recurring musical phrase used as an element of musical structure