The possibility of storing energy efficiently and sustainably at little cost is crucial to prevent climate change and the exhaustion of natural resources. In this work we demonstrate that interconnected and porous carbon fibers easily obtained from lignin exhibit ultrafast charge–discharge and excellent energy density and cyclability performances, to be used as binderless and flexible electrodes in supercapacitors. ; Financial support by the Spanish Ministerio de Economía y Competitividad, for the MAT2013-42007-P, P09-FQM-5156R, CTQ2012-36408, JCI2011-10566, JCI-2012-12664 and the joint Spanish-Japanese (PRI-PIBJP-2011-0766) projects, FEDER and the Junta de Andalucía is gratefully acknowledged.