Potassium-ion (K-ion) batteries can be an attractive alternative for grid-scale energy storage due to the abundance of K resources. For the first time, we designed and fabricated a non-aqueous K-ion battery (KIB) by employing 3,4,9,10-perylene–tetracarboxylicacid–dianhydride (PTCDA) as the cathode. The PTCDA electrode exhibits a high capacity of 131mAhg−1 in the potential range of 1.5–3.5V vs. K/K+, which corresponds to the insertion of two K ions per PTCDA molecule. The PTCDA cathode also shows great cycling performance, with a capacity retention of 66.1% over 200 cycles. Furthermore, K11PTCDA can be obtained when discharging PTCDA to 0.01V vs. K/K+, which delivers a high capacity of 753mAhg−1. The excellent electrochemical performance makes PTCDA a promising organic electrode based on K-ion chemistry for grid-scale energy storage.