公众（英语：Public），是一个社会学上的概念，基本意义是指包含自己在内的社会整体；但为了公平性起见，在实务运作方面通常会产生「排己性」，也就是去除自己及亲近团体（如亲戚、朋友、同事等）。相近的概念包括人民、大众、群众等。 例如公共开支、公共财产、公共汽车等。

具体而言，公众可再分层、分类。 Aggens 在1983年的研究文章提及，原文: "Identifying different levels of public interest in participation" 还有 "There is no single public, but different levels of public based on differing levels of interest and ability"。

In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of such groupings. This is a different concept to the sociological concept of the Öffentlichkeit or public sphere. The concept of a public has also been defined in political science, psychology, marketing, and advertising. In public relations and communication science, it is one of the more ambiguous concepts in the field. Although it has definitions in the theory of the field that have been formulated from the early 20th century onwards, it has suffered in more recent years from being blurred, as a result of conflation of the idea of a public with the notions of audience, market segment, community, constituency, and stakeholder.