The chiral valley is a two-dimensional topological electronic structure that can be found in graphene, a one-atom-thick sheet of carbon atoms arranged in a hexagonal lattice. The chiral valley refers to the two-fold degenerate energy bands that touch each other at a specific point in the Brillouin zone, known as the Dirac point. These energy bands are associated with electrons and holes with opposite chiralities, which are analogous to the left and right-handed states of particles. The presence of the chiral valley in graphene gives rise to unique electronic and optical properties, such as the valley-dependent Hall effect and circular dichroism, which have potential applications in future electronics and optoelectronics devices.