The Exclusive Brethren are a subset of the Christian evangelical movement generally described as the Plymouth Brethren. They are distinguished from the Open Brethren from whom they separated in 1848.

The Exclusive Brethren are now spread into a number of locations, most of which differ on minor points of doctrine or practice. One organization that originated from the Exclusive Brethen, made famous through media attention, is the Raven-Taylor-Hales group, now known as the Plymouth Brethren Christian Church, which maintains the doctrine of uncompromising separation from the world based on their interpretation of 2 Corinthians 6 and 2 Timothy 2, believing that attendance at the Communion Service, the 'Lord's Supper', governs and strictly limits their relationship with others, even other Brethren groups.

The Brethren groups have one fellowship in some 19 countries – including France, Brazil, Germany, Spain, Italy, Denmark, the Netherlands, Switzerland, Sweden, Argentina, Jamaica, Barbados, St Vincent and the Grenadines, but they are more numerous in Australia, New Zealand, the United Kingdom, and North America, where they are referred to as the Exclusive Brethren or just the Brethren.

The Plymouth Brethren split into Exclusive and Open Brethren in 1848 when George Müller refused to accept John Nelson Darby's view of the relationship between local assemblies following difficulties in the Plymouth meeting. Brethren that held Muller's congregational view became known as "Open", those holding Darby's 'connexional' view, became known as "Exclusive" or "Darbyite" Brethren.^{[citation needed]}

Darby's circular on 26 August 1848, cutting off not only Bethesda but all assemblies who received anyone who had ever attended Bethesda, was to define the essential characteristic of "exclusivism" that he was to pursue for the rest of his life. He set it out in detail in a pamphlet he issued in 1853 entitled Separation from Evil – God's Principle of Unity. But a tension had existed since the earliest times, as set out in a letter from Anthony Norris Groves in 1836 to Darby (who was not a believer in adult baptism):

Some will not have me hold communion with the Scotts, because their views are not satisfactory about the Lord's Supper; others with you, because of your views about baptism; others with the Church of England, because of her thoughts about ministry. On my principles, I receive them all; but on the principle of witnessing against evil, I should reject them all.

For most of his life, Darby was able to hold the exclusives together, although several longtime members had seceded after accusing him of similar errors about the nature of Christ's humanity of which he had accused Benjamin Wills Newton. The Central Meeting in London (London Bridge) would communicate with the other assemblies and most difficulties were eventually smoothed over.^{[citation needed]}

But shortly before he died in 1882, things started to fall apart. It all started from an initiative in 1879 of Edward Cronin, one of the Dublin founding members, that paralleled Darby's initiation of a new assembly at Plymouth thirty years before. Some members had left a failing assembly in Ryde and Cronin travelled down to break bread with them. When he reported back to London, different assemblies took differing views of his action. Though Darby was sympathetic in private he attacked him fiercely in public. By 1881 an assembly in Ramsgate had itself split over the issue and the division, over an issue not of doctrine or principle but church governance, became irrevocable.