Irish traditional music (also known as Irish trad, Irish folk music, and other variants) is a genre of folk music that developed in Ireland.

In A History of Irish Music (1905), W. H. Grattan Flood wrote that, in Gaelic Ireland, there were at least ten instruments in general use. These were the crwth (a small rubbed strings harp) and cláirseach (a bigger harp with typically 30 strings), the tiompán (a small string instrument played with a bow or plectrum), the feadán (a fife), the buinne (an oboe or flute), the guthbuinne (a bassoon-type horn), the beannbhuabhal and corn (hornpipes), the cuislenna (bagpipes – see Great Irish warpipes), the stoc and storgán (clarions or trumpets), and the cnámha (bones). Within the tradition, there is poetic reference to the use of a fiddle as far back as the 7th century,, which predates the development of the modern violin by around 900 years.

There are several collections of Irish folk music from the 18th century, but it was not until the 19th century that ballad printers became established in Dublin. Important collectors include Colm Ó Lochlainn, George Petrie, Edward Bunting, Francis O'Neill, James Goodman and many others. Though solo performance is preferred in the folk tradition, bands or at least small ensembles have probably been a part of Irish music since at least the mid-19th century, although this is a point of much contention among ethnomusicologists.

Irish traditional music has endured more strongly against the forces of cinema, radio and the mass media than the indigenous folk music of most countries in the west of Europe. From the end of the Second World War until the late fifties folk music was held in low regard. Comhaltas Ceoltóirí Éireann (an Irish traditional music association) and the popularity of the Fleadh Cheoil (music festival) helped lead the revival of the music. Following the success of the Clancy Brothers and Tommy Makem in the US in 1959, Irish folk music became fashionable again. The lush sentimental style of singers such as Delia Murphy was replaced by guitar-driven male groups such as the Dubliners. Irish showbands presented a mixture of pop music and folk dance tunes, though these died out during the seventies. The international success of the Chieftains and subsequent musicians and groups has made Irish folk music a global brand.

Historically much old-time music of the US grew out of the music of Ireland, England and Scotland, as a result of cultural diffusion. By the 1970s Irish traditional music was again influencing music in the US and further afield in Australia and Europe. It has occasionally been fused with rock and roll, punk rock and other genres.

Irish dance music is isometric; is built around patterns of bar-long melodic phrases akin to call and response. A common pattern is A Phrase, B Phrase, A Phrase, Partial Resolution, A Phrase, B Phrase, A Phrase, Final Resolution, though this is not universal. Mazurkas, for example, tend to feature a C Phrase instead of a repeated A Phrase before the Partial and Final Resolutions. Many tunes have pickup notes which lead in to the beginning of the A or B parts. Mazurkas and hornpipes have a swing feel, while other tunes have straight feels.

Tunes are typically binary in form, divided into two (or sometimes more) parts, each with four to eight bars. The parts are referred to as the A-part, B-part, and so on. Each part is played twice, and the entire tune is played three times; AABB, AABB, AABB. Many tunes have similar ending phrases for both A and B parts; it is common for hornpipes to have the second half of each part be identical. Additionally, hornpipes often have three quavers or quarternotes at the end of each part, followed by pickup notes to lead back to the beginning of the A part onto the B part. Many airs have an AABA form.

While airs are usually played singly, dance tunes are usually played in medleys of 2-4 tunes called sets.