古斯塔夫·勒庞（Gustave Le Bon，1841—1931），法国社会心理学家。从1894年开始，勒庞发表了一系列社会心理学著作，主要有《民族进化的心理定律》（1894年）、《乌合之众》（1895年）、《社会主义心理学》（1898年）《革命心理学》（191 2年）以及《战争心理学》（1916年）等。

是一本研究大众心理学的著作。在书中，勒庞阐述了群体以及群体心理的特征，指出了当个人是一个孤立的个体时，他有着自己鲜明的个性化特征，而当这个人融入了群体后，他的所有个性都会被这个群体所淹没，他的思想立刻就会被群体的思想所取代。而当一个群体存在时，他就有着情绪化、无异议、低智商等特征。

A psychological crowd once constituted, it acquires certain provisional but determinable general characteristics. To these general characteristics there are adjoined particular characteristics which vary according to the elements of which the crowd is composed, and may modify its mental constitution. Psychological crowds, then, are susceptible of classification; and when we come to occupy ourselves with this matter, we shall see that a heterogeneous crowd—that is, a crowd composed of dissimilar elements—presents certain characteristics in common with homogeneous crowds—that is, with crowds composed of elements more or less akin (sects, castes, and classes)—and side by side with these common characteristics particularities which permit of the two kinds of crowds being differentiated.
But before occupying ourselves with the different categories of crowds, we must first of all examine the characteristics common to them all. We shall set to work like the naturalist, who begins by describing the general characteristics common to all the members of a family before concerning himself with the particular characteristics which allow the differentiation of the genera and species that the family includes.