The　design　and　application　of　electrocatalysts　based　on　Earth-abundant　transition-metal　oxides　for　biomass　valorization　remain　relatively　underexplored.　Here,　we　report　a　nanocasting　route　to　synthesize　mesoporous　delta-MnO2　with　a　high　surface　area　(198　m(2)/g),　high　pore　volume,　and　narrow　pore　size　distributions　to　address　this　issue.　By　taking　structural　advantages　of　mesoporous　oxides,　this　mesoporous　delta-MnO2　is　employed　as　a　highly　efficient,　selective,　and　robust　anode　for　5-hydroxymethylfurfural　(HMF)　electrochemical　oxidation　to　2,5-furandicarboxylic　acid　(FDCA)　with　a　high　yield　(98%)　and　faradic　efficiency　(98%)　under　alkaline　conditions.　The　electrocatalyst　is　also　effective　for　the　more　difficult　HMF　electro-oxidation　under　acidic　conditions,　forming　both　FDCA　and　maleic　acid　as　value-added　products　in　a　potential-dependent　manner.　Experimental　results　combined　with　theoretical　calculations　provide　insights　into　the　reaction　kinetics　and　the　reaction　pathways　of　electrochemical　HMF　oxidation　over　this　advanced　electrocatalyst.　This　work　thus　showcases　the　rational　design　of　non-noble　metal　electrodes　for　multiple　applications,　such　as　oxygen　evolution,　water　electrolysis,　and　biomass　upgrading　with　high　energy　efficiency.