Every megalithic tomb in the State's Sites and Monuments Record, 1616 of them, by type and county: the townland, a line from the surveyors' own description, and a link to the official record.
In their 1961 survey of megalithic tombs in Ireland, Seán Ó Nualláin and Rúaidhrí de Valera described four categories: court cairns, portal dolmens, wedge-shaped gallery graves and passage tombs. The Sites and Monuments Record uses the same four, plus "unclassified" for tombs it cannot assign. (Wikipedia, "Passage grave" ↗)
Court tombs are Neolithic tombs with an open courtyard leading to one or more roofed, partitioned burial chambers. More than 390 were built in Ireland (and over 100 in south-west Scotland) in about 3900 to 3500 BC; many were built in phases and reused in the Early Bronze Age. (Wikipedia, "Court cairn" ↗)
Portal tombs (dolmens, dolmain) have a single chamber: two or more upright stones carrying a large flat capstone. Most date from the Neolithic, between about 4000 and 3000 BC, and some were once covered by a mound that has since worn away, leaving the stone "skeleton". (Wikipedia, "Dolmen" ↗)
Passage tombs have one or more burial chambers under a mound of earth or stone, reached by a narrow passage of large stones. Of the Irish types, only passage tombs are widespread across Europe, and in Ireland and Britain they often stand in clusters, called passage tomb cemeteries. (Wikipedia, "Passage grave" ↗)
Wedge tombs are named for a burial chamber that narrows, usually from west to east, in both height and width; the gallery is double-walled. They were built between the late Neolithic and the middle Bronze Age, about 2500 to 2000 BC, and between 500 and 550 are known in Ireland, mostly in the west and north-west. (Wikipedia, "Gallery grave" ↗)
Republic: Sites and Monuments Record classes "Megalithic tomb - court tomb", "- portal tomb", "- passage tomb", "- wedge tomb" and "- unclassified", not counting 1 "present location" record. Records classed "Megalithic structure" are not counted. Northern Ireland (605: 117 court, 54 portal, 28 passage, 66 wedge, 340 unclassified): NISMR records of type MEGALITHIC TOMB, split by a type word (court, portal, passage, wedge) in the record's description; the rest are under "unclassified". That split is a keyword match, not the NISMR's own classification, and includes possible and unlocated tombs.
County by county
Open a county for every record: townland, a line quoted from the survey's own description where it has one, the SMR number (linked to the Historic Environment Viewer) and a map link where the record has a position.
County Antrim· 174 in the Northern Ireland record (23 court tomb, 5 portal tomb, 10 passage tomb, 14 wedge tomb, 122 unclassified) (count only)
A record is a survey entry, not a promise that something is there. The Sites and Monuments Record lists sites that are known, reported or marked on old maps, including some that have been destroyed, moved, or were never found when inspected. Each record's own description says what the surveyors saw; read it before you set out.
A present location record is where a moved object (in a church, a museum, a school, a garden) is now. The place it was found or first stood usually has a record of its own, so one object can appear twice.
Some records have no description uploaded yet, and a few have no usable position; they are marked as such.
The Sites and Monuments Record covers the Republic only. Northern Ireland's record (the NISMR) is counted here by county from its open data, by matching the record descriptions; it is not listed site by site and its counts are not directly comparable.
Type names differ between sources: a portal tomb is the same thing as a portal dolmen or dolmen, a court tomb as a court cairn, and a wedge tomb as a wedge-shaped gallery grave. The record's own class is what is counted here.
Wikipedia's figures for the island as a whole (over 390 court tombs, 500 to 550 wedge tombs) are not the same thing as the counts here, which are the Republic's record only, by the survey's own classes.
Quick answersHow many megalithic tombs are there in Ireland?
The Sites and Monuments Record lists 1616 in the Republic: 525 wedge tombs, 305 court tombs, 204 passage tombs, 150 portal tombs and 432 the survey has not assigned to a type. Northern Ireland's record has 605 records typed "megalithic tomb", including possible and unlocated ones.
Which county has the most megalithic tombs?
On the record, Sligo (237), then Donegal (235) and Mayo (203). By type: most wedge tombs are in Clare (155), most court tombs in Mayo (85), most passage tombs in Sligo (78) and most portal tombs in Donegal (31).
What are the four types of Irish megalithic tomb?
Court tombs, portal tombs (dolmens), passage tombs and wedge tombs, the four categories Seán Ó Nualláin and Rúaidhrí de Valera used in their 1961 survey of Irish megalithic tombs.