广场恐惧症是一种焦虑症，患者会害怕人群拥挤的情况，尤其是在封闭的空间当中，而且通常会引发恐慌症状。因此，广场恐惧症患者通常待在家里面，对外出则感到困难。

英语中广场恐惧症（Agoraphobia）这个字是来自希腊字agora（αγορά）和phobos（φόβος）。这个字在现代希腊文中被翻译成「广场恐惧症」。一个普遍的、错误的观念是广场恐惧症是恐惧一些公开的地方。但其实通常患有这个病的人不是怕这些地方的本身（即不是怕多人的本质），而是怕一些与这些地方有关联的公众场合或处境。希腊字眼agora有「一群人聚集」的意思（拉丁文里的forum），意思是一个很热闹的广场，而不是一个公开的地方，令人容易区别agoraphobia和claustrophobia这两个英文本。

Agoraphobia is an anxiety disorder characterized by anxiety symptoms in reaction to situations where the sufferer perceives the environment to be dangerous, uncomfortable, or unsafe. These situations can include wide-open spaces, uncontrollable social situations, unfamiliar places, shopping malls, airports, and bridges. The term "agoraphobia" was coined by the German psychiatrist Carl Friedrich Otto Westphal, from Greek ἀγορά, meaning "large public square/marketplace" and -φοβία, -phobia, meaning "fear". Agoraphobia is defined within the DSM-IV TR as a subset of panic disorder, involving the fear of incurring a panic attack in those environments. In the DSM-5, however, agoraphobia is classified as being separate from panic disorder. The sufferers may go to great lengths to avoid those situations, in severe cases becoming unable to leave their homes or safe havens.