草根（英语：Grassroots），或草根阶层，源自英语名词，是个借词。指的是在社会阶层中的一般中低收入的平民百姓、群众。他们的个人势力较弱，但是人数众多。这些特征与政府、统治阶级、大型企业或其它社会强手的特征对立。

草根象征着社会低层，但概念和较狭义的无产阶级有关但又有别的，即使用这词语时不指涉特定的职业(蓝领)，也因为现代普选的推行，不可以用赋税的多少决定是否资产阶级。

草根运动是指一种非常规从低层势力而启发的运动。社会上的变化通常是由有势力实体（如政府）启发或操作的，草根运动在此是指群众启发的运动。同样的在商业领域里，市场中的变化通常是由大型企业领导的，草根运动在此是指由消费者启发的市场变化。

A grassroots movement (often referenced in the context of a political movement) as defined by Webster's Third International Dictionary, is one which uses the people in a given district as the basis for a political or economic movement. Grassroots movements and organizations utilize collective action from the local level to affect change at the local, regional, national, or international level. Grassroots movements are associated with bottom-up, rather than top-down decision making, and are sometimes considered more natural or spontaneous than more traditional power structures. Grassroots movements utilize a variety of strategies from fundraising and registering voters, to simply encouraging political conversation. Goals of specific movements vary, but the movements are consistent in their focus on increasing mass participation in politics.