会计网络或会计协会是一个专业的服务网络，其主要目的是为会员提供资源，以帮助世界各地的客户，从而通过汇集更多的资源来解决一个问题，从而减少不确定性。这些网络和协会独立于独立成员运作。其中的会计网络被称为“四大”。
“四大”是对全球四大专业服务网络的统称，包括全球会计网络德勤、安永、毕马威和普华永道。这四个网络通常被组合在一起的原因有很多:它们的规模相对于市场的其他部分是可比性的，无论是在收入方面还是劳动力方面;它们在向其客户提供广泛专业服务的能力方面被认为是平等的;而且，在那些希望在专业服务行业(尤其是会计行业)开始职业生涯的人当中，他们被认为是同样有吸引力的工作圈子，因为这些公司与《财富》500强公司接触的频率很高。
四大会计师事务所都为客户提供审计、担保、税务、管理咨询、精算、公司财务和法律服务。大多数对上市公司的审计，以及许多对私营公司的审计，都是由这四个网络进行的。
直到20世纪后期，专业服务市场实际上是由八大网络主导的，它们被戏称为“八大网络”。八大会计师事务所包括安达信(Arthur Andersen)、安永信(Arthur Young)、普华永道(Coopers & Lybrand)、德勤(Deloitte Haskins and Sells)、安永会计师事务所(Ernst & Whinney)、Peat Marwick Mitchell、普华永道(Price Waterhouse)和Touche Ross。
由于这些公司的合并，以及2002年安达信(Arthur Andersen)的倒闭，“八大”逐渐减少，在21世纪之交，四大网络主宰了市场。
An accounting network or accounting association is a professional services network whose principal purpose is to provide members resources to assist the clients around the world and hence reduce the uncertainty by bringing together a greater number of resources to work on a problem. The networks and associations operate independently of the independent members. The largest accounting networks are known as the Big Four.
The Big Four is the nickname used to refer collectively to the four largest professional services networks in the world, consisting of the global accounting networks Deloitte, Ernst & Young (EY), KPMG and PricewaterhouseCoopers (PwC). The four networks are often grouped together for a number of reasons: they are each comparable in size relative to the rest of the market, both in terms of revenue and workforce; they are each considered equal in their ability to provide a wide scope of professional services to their clients; and, among those looking to start a career in professional services, particularly accounting, they are considered equally attractive networks to work in, because of the frequency with which these firms engage with Fortune 500 companies.
The Big Four each offer audit, assurance, taxation, management consulting, actuarial, corporate finance, and legal services to their clients. A significant majority of the audits of public companies, as well as many audits of private companies, are conducted by these four networks.
Until the late 20th century, the market for professional services was actually dominated by eight networks which were nicknamed the "Big 8". The Big Eight consisted of Arthur Andersen, Arthur Young, Coopers & Lybrand, Deloitte Haskins and Sells, Ernst & Whinney, Peat Marwick Mitchell, Price Waterhouse, and Touche Ross.
The Big Eight gradually reduced due to mergers between these firms, as well as the 2002 collapse of Arthur Andersen, leaving four networks dominating the market at the turn of the 21st century.