Flexible composites with manganese oxides (MnOx) nanocrystals encapsulated in electropun carbon nanofibers were successfully fabricated via a simple and practical combination of electrospinning and carbonization process. The as-formed MnOx/carbon nanofibers composites have a rough surface with MnOx nanoparticles well embedded in the carbon nanofibers backbones. When used as electrodes for supercapacitor, the resulting MnOx/carbon nanofiber composites exhibit good electrochemical performance with a specific capacitance of 174.8 F g(-1) at 2 mV s(-1) in 0.5 M Na2SO4 electrolyte, a good rate capability at high current density and long-term cycling stability. It is expected that such freestanding composites could be promising electrodes for high-performance supercapacitors. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.