Celtic rock is a genre of folk rock and a form of Celtic fusion which incorporates Celtic music, instrumentation and themes into a rock music context. It has been extremely prolific since the early 1970s and can be seen as a key foundation of the development of highly successful mainstream Celtic bands and popular musical performers, as well as creating important derivatives through further fusions. It has played a major role in the maintenance and definition of regional and national identities and in fostering a pan-Celtic culture. It has also helped to communicate those cultures to external audiences.

The style of music is the hybrid of traditional Irish, Scottish Gaelic and Breton musical forms with rock music. This has been achieved by the playing of traditional music, particularly ballads, jigs and reels with rock instrumentation; by the addition of traditional Celtic instruments, including the Celtic harp, tin whistle, uilleann pipes (or Irish Bagpipes), fiddle, bodhrán, accordion, concertina, melodeon, and bagpipes (highland) to conventional rock formats; by the use of lyrics in native Celtic languages or dialects and by the use of traditional rhythms and cadences in otherwise conventional rock music. Just as the validity of the term Celtic in general and as a musical label is disputed, the term Celtic rock cannot be taken to mean there was a unified Celtic musical culture between the Celtic nations. However, the term has remained useful as a means of describing the spread, adaptation and further development of the musical form in different but related contexts.