Classical and quantum chiral order in frustrated XY magnets

Recent studies on the chiral order of regularly frustrated XY magnets are reviewed both in classical and quantum cases. In the classical case, chiral transition is a thermal one, while in the quantum case, it is a quantum phase transition. Importance of spatial dimensionality on the chiral order is clarified. Particular attention is paid to the possible ``spin-chirality decoupling’’ phenomenon, and to the possible pure chiral phase of either thermal or quantum origin where the chirality exhibits a long-range order without the standard spin order.