工人阶级（又称劳动阶级、劳动阶层等；英文：working class）通常用于表示社会地位与社会等级，无论何时，该阶层在社会所占比例最高，但是随着经济的发展，比例减少，一般为产业工人阶层为主。该术语没有一致的解释，主要依赖个人的立场与观点的不同来理解。比如美国划分阶级标准是依照经常性收入和就业率来确定。

马克思主义认为，工人阶级（即无产阶级）是那些靠出卖劳动力（包括体力和脑力）、不拥有生产资料，劳动成果大部分被资产阶级剥削，并为社会创造主要财富的阶层，包括大部分的体力和脑力劳动者。

The working class (also labouring class and proletariat) is the people employed for wages, especially in manual-labour occupations and in skilled, industrial work. Working-class occupations include blue-collar jobs, some white-collar jobs, and most service-work jobs. The working class only rely upon their earnings from wage labour, thereby, the category includes most of the working population of industrialized economies, of the urban areas (cities, towns, villages) of non-industrialized economies, and of the rural workforce.