The authors demonstrate that 100% light absorption can be achieved in a single patterned sheet of doped graphene. They show that a planar array of small lossy particles, such as doped graphene nanodisks, can exhibit full absorption under critical-coupling conditions if the cross section of each particle is comparable to the area of the lattice unit cell. Specifically, arrays of doped graphene nanodisks display full absorption when supported on a substrate under total internal reflection (TIR) or when lying on a dielectric layer coating a metal. The study provides insights into the optical response of graphene nanodisks and the universal limit to absorption by a thin layer. The results have implications for infrared light detectors and sources, which can be made tunable via electrostatic doping of graphene.The authors demonstrate that 100% light absorption can be achieved in a single patterned sheet of doped graphene. They show that a planar array of small lossy particles, such as doped graphene nanodisks, can exhibit full absorption under critical-coupling conditions if the cross section of each particle is comparable to the area of the lattice unit cell. Specifically, arrays of doped graphene nanodisks display full absorption when supported on a substrate under total internal reflection (TIR) or when lying on a dielectric layer coating a metal. The study provides insights into the optical response of graphene nanodisks and the universal limit to absorption by a thin layer. The results have implications for infrared light detectors and sources, which can be made tunable via electrostatic doping of graphene.