Today, the Reformed Presbyterian Church of Ireland is a relatively small denomination of some 40 congregations, most of which are in counties Antrim, Down and Londonderry and others in counties Armagh, Donegal, Galway, Monaghan and Tyrone. Reformed Presbyterians are also known as Covenanters because of their adherence to the National Covenant of 1638 and the Solemn League and Covenant of 1643.

This essay provides a broad overview of the origins and early history of the Reformed Presbyterian Church of Ireland and, in what is very much a work in progress, discusses the sources that are available for the study of its members and adherents.