Arithmomania is a mental disorder that may be seen as an expression of obsessive–compulsive disorder (OCD). Sufferers from this disorder have a strong need to count their actions or objects in their surroundings.
Sufferers may for instance feel compelled to count the steps while ascending or descending a flight of stairs or to count the number of letters in words. They often feel it is necessary to perform an action a certain number of times to prevent alleged calamities. Other examples include counting tiles on the floor or ceiling, the number of lines on the highway, or simply the number of times one breathes or blinks.
Arithmomania sometimes develops into a complex system in which the sufferer assigns values or numbers to people, objects and events in order to deduce their coherence.
Counting may be done aloud or in thought.
In popular culture 
- Folklore concerning vampires often depicts them with arithmomania, such as a compulsion to count seeds or grains of rice. More lightheartedly, the Muppet Count von Count from Sesame Street appears to be a fellow "sufferer".
- The protagonist of the film Stranger Than Fiction appears to suffer from arithmomania about certain things, such as counting strokes of his toothbrush.
- Archie Comics' Forsythe (Jughead) Jones has been portrayed as a sufferer of arithmomania.
- The online game Lost Souls has a game version of arithmomania, consisting of an impulse to count objects in one's environment. Discordians with arithmomania are more likely to count in a manner similar to Count von Count.
- The character Adrian Monk of the TV series Monk shows arithmomania as part of his obsessive compulsive disorder, including counting poles along a footpath, and counting the number of phobias he has.
- The character Fudge from the Judy Blume series of the same name seems to be afflicted by this in that he must eat 200 cheerios each morning
- Yaryura-Tobias, José A.; Neziroglu, Fugen A. (1997). Obsessive-compulsive disorder spectrum: pathogenesis, diagnosis, and treatment. American Psychiatric Publishing. p. 12. ISBN 0-88048-707-0. "Arithmomania, a common form, causes patients to engage in addition, division, subtraction and multiplication endlessly."
- Schiffer, Randolph B.; Rao, Stephen M.; Fogel, Barry S. (2003). Neuropsychiatry: A Comprehensive Textbook, Second Edition. Lippincott Williams & Wilkins. p. 948. ISBN 0-7817-2655-7. "Charcot, however, was the first to identify the involuntary "impulsive" ideas, such as doubting mania, double checking, touching, and arithmomania (an obsession with counting and numbers), as part of GTS and to link them to the impulsive movements."
- Yaryura-Tobias, José A.; Neziroglu, Fugen A. (1997). Obsessive-compulsive disorder spectrum: pathogenesis, diagnosis, and treatment. American Psychiatric Pulishing. p. 12. ISBN 0-88048-707-0. "An ideational compulsion is an urge to perform an act in one's mind (e.g. arithmomania, onomatomania)."
- Barber, Vampires, Burial and Death, p. 49.
- "Arithmomania - LSWiki". Retrieved 2010-03-22. "Arithmomania is a mental disorder that manifests as an obsession with counting. As it appears in Lost Souls, this is limited to counting objects in one's environment."