This manuscript presents a single-layer quadruple-band millimeter-wave antenna for 5G application. Its upper layer is made up of a hexagonal patch fed by a 50 Ω microstrip line. By etching two symmetric split-ring slots on the hexagonal patch, it allows to operate at three frequencies which are 27.5 GHz, 44.6 GHz, and 50.7 GHz. Then, a pair of L-shaped branches are coupled on both sides of the microstrip line to realize the resonance point of 36.7 GHz. The gains at these four frequencies respectively are 6.4 dBi, 7.6 dBi, 9.2 dBi, and 7.1 dBi while the -10 dB impendence bandwidth cover 27.2 GHz-27.8 GHz, 37.3 GHz-37.6 GHz, 44.3 GHz-44.9 GHz, and 50.1-51.7 GHz. These results indicate that the proposed antenna is a promising candidate for 5G millimeter-wave applications.