协会是指由个人、单个组织为达到某种目标，通过签署协议，自愿组成的团体或组织。

中文中「协会」一词蕴涵英文Association与Cooperative之义，在日文与韩文中，皆分别用组合和协同组合表示。

协会和工会组织的概念不同。“协会”常指包括职业、雇主、行业、学术和科学等方面为达成某种目标而成立的组织。“工会”多指被雇用者为确保自身权益（特别是经济利益）而成立的组织，多集中于雇佣者和被雇佣者的关系。

A voluntary group or union (also sometimes called a voluntary organization, common-interest association, or just an association) is a group of individuals who enter into an agreement as volunteers to form a body (or organization) to accomplish a purpose. Common examples include trade associations, trade unions, learned societies and professional associations, environmental groups, and various other types of groups. Membership is not necessarily voluntary, as it may be effectively required in order to work, which is why some people use the term common-interest association to describe groups which form out of a common interest although this term is not widely used or understood. Voluntary Associations may be incorporated or unincorporated; for example, in the United States associations gained additional powers by incorporating. In the UK the term Voluntary Association/Voluntary Organisation covers every type of group from a small local Residents' Association to large Associations (often Registered Charities) with multimillion-pound turnover and running large scale business operations (often providing some kind of public service as sub-contrators to government departments or Local Authorities).