Potassium-ion batteries (PIBs) are in the spotlight as a possible alternative to lithium-ion batteries. Graphitic carbons are promising anode materials for PIBs due to their low-plateau potential that is beneficial for the realization of high-voltage full cells. However, inferior cycling stability hinders their practical application. Herein, highly graphitized carbon nanofibers (HG-CNFs) as a free-standing electrode are served as the anode for PIBs. The HG-CNFs exhibits a reversible capacity of 200 mAh g(-1) at the plateau potential below 0.2 V (76% of total capacity) and superior rate performance with a depotassiation capacity of 226 mAh g(-1) at 35 C. Moreover, the capacity decay of HG-CNFs is less than 0.008% per cycle during 400 cycles, which is superior to those of most other graphitic carbons. The excellent electrochemical performance of HG-CNFs is attributed to its merits of freestanding fibrous networks and graphitic structure with rational defects that alleviate the volume expansion incurred by K+ intercalation.