R-L21 or R1b1a2a1a2c, also known as R-M529 or R-S145, is a Human Y-chromosome DNA haplogroup. It is often linked to the Celtic peoples, and their migrations into Western Europe, during the Bronze and Iron Ages. One subclade, R-DF13 is numerically dominant amongst both bearers of R-L21 in general, and among living males in England, Ireland, Scotland, and Wales.