Although many of the manuscripts have not survived and much more material was probably never committed to writing, there is enough remaining to enable the identification of distinct, if overlapping, cycles: the Mythological Cycle, the Ulster Cycle, the Fenian Cycle and the Historical Cycle.
Aínda que moitos dos manuscritos non lograron sobrevivir e moitos materiais probablemente nunca chegaron a ser escritos, hai contidos abondos para permitir a identificación de catro ciclos distintos: o Ciclo mitolóxico, o Ciclo do Ulster, o Ciclo feniano e o Ciclo histórico.