Hoplophobia is a political neologism coined by retired American military officer Jeff Cooper as a pejorative to describe an "irrational aversion to weapons." It is also used to describe the "fear of firearms" or the "fear of armed citizens." Hoplophobia is a political term and not a recognized medical phobia.

Phobias are a common form of anxiety disorders and distributions are heterogeneous by age and gender. An American study by the National Institute of Mental Health (NIMH) found that between 8.7 percent and 18.1 percent of Americans suffer from phobias, making it the most common mental illness among women in all age groups and the second most common illness among men older than 25. Between 4 percent and 10 percent of all children experience specific phobias during their lives, and social phobias occur in one percent to three percent of children and adolescents.

A Swedish study found that females have a higher incidence than males (26.5 percent for females and 12.4 percent for males). Among adults, 21.2 percent of women and 10.9 percent of men have a single specific phobia, while multiple phobias occur in 5.4 percent of females and 1.5 percent of males. Women are nearly four times as likely as men to have a fear of animals (12.1 percent in women and 3.3 percent in men) — a higher dimorphic than with all specific or generalized phobias or social phobias. Social phobias are more common in girls than in boys, while situational phobia occurs in 17.4 percent of women and 8.5 percent of men.

The terms "distress" and "impairment" as defined by the "Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition" (DSM-IV-TR) should also take into account the context of the person's environment if attempting a diagnosis. The DSM-IV-TR states that if a feared stimulus, whether it be an object or a social situation, is absent entirely in an environment, a diagnosis cannot be made. An example of this situation would be an individual who has a fear of mice but lives in an area devoid of mice. Even though the concept of mice causes marked distress and impairment within the individual, because the individual does not usually encounter mice, no actual distress or impairment is ever experienced. Proximity to, and ability to escape from, the stimulus should also be considered. As the phobic person approaches a feared stimulus, anxiety levels increase, and the degree to which the person perceives they might escape from the stimulus affects the intensity of fear in instances such as riding an elevator (e.g. anxiety increases at the midway point between floors and decreases when the floor is reached and the doors open).

American firearms expert and retired Marine colonel Jeff Cooper coined the word in 1962 to denigrate and anger proponents of gun control by implying that their thoughts were "aberrant" and unreasoning:

I coined the term "hoplophobia" in 1962 in response to a perceived need for a word to describe a mental aberration consisting of an unreasoning terror of gadgetry, specifically, weapons. The most common manifestation of hoplophobia is the idea that instruments possess a will of their own, apart from that of their user. This is not a reasoned position, but when you point this out to a hoplophobe he is not impressed because his is an unreasonable position. To convince a man that he is not making sense is not to change his viewpoint but rather to make an enemy. Thus hoplophobia is a useful word, but as with all words, it should be used correctly.

The term was constructed from the Greek ὅπλον – "hoplon", meaning, amongst other things, "arms," and φόβος – "phobos", meaning "fear." Cooper employed the term as just another alternative to other slang terms, stating: "We read of 'gun grabbers' and 'anti-gun nuts' but these slang terms do not [explain this behavior]." Cooper's conjecture was that "the most common manifestation of hoplophobia is the idea that instruments possess a will of their own, apart from that of their user." Writing in an opinion piece, "Pittsburgh Tribune-Review" columnist Dimitri Vassilaros said that the term was intended by Cooper as tongue-in-cheek to mock those who think guns have free will.