The Giant's Causeway (Irish: Clochán an Aifir)[1] is an area of approximately 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption.

[3][4] It is located in County Antrim on the north coast of Northern Ireland, about three miles (4.8 km) northeast of the town of Bushmills.

It was declared a World Heritage Site by UNESCO in 1986 and a national nature reserve by the Department of the Environment for Northern Ireland in 1987.

[11] In respect of its key role in the development of volcanology as a geoscience discipline, and notably the origin of basalt, the Palaeocene rocks of the Giant's Causeway and Causeway Coast were included by the International Union of Geological Sciences (IUGS) in its assemblage of 100 "geological heritage sites" around the world in a listing published in October 2022.

[14] Across the sea, there are identical basalt columns (a part of the same ancient lava flow) at Fingal's Cave on the Scottish isle of Staffa, and it is possible that the story was influenced by this.

[15] Overall, in Irish mythology, Fionn mac Cumhaill is not a giant, but a hero with supernatural abilities, contrary to what this particular legend may suggest.

[18] Letitia Elizabeth Landon comments on these mythological associations in her notes to The Giant's Causeway., a poetical illustration to a painting by Thomas Mann Baynes.

The existence of the causeway was announced to the wider world the following year by the presentation of a paper to the Royal Society from Sir Richard Bulkeley, a fellow of Trinity College, Dublin.

[21] In the caption to the plates, French geologist Nicolas Desmarest suggested, for the first time in print, that such structures were volcanic in origin.

[27][28] Ultimately, the private developer dropped a legal challenge to the publicly funded plan,[29] and the new visitor centre was officially opened by 2012.

[37] An online campaign to remove creationist material was launched in 2012, and following this, the Trust carried out a review and concluded that they should be amended to have the scientific explanation on the origin of the causeway as their primary emphasis.

There is a scenic walk of 7 miles (11 km) from Portrush alongside Dunluce Castle and the Giant's Causeway and Bushmills Railway.