Molybdenum　disulfide　(MoS2),　which　is　a　two-dimensional　transition　metal　chalcogenide,　has　been　considered　to　have　great　lithium/sodium　storage　potential.　However,　its　poor　conductivity,　unsatisfactory　mechanical　stability　and　large　volume　change　upon　cycling　make　MoS2　not　well　applied　in　practice.　Herein,　MoS2@C　nanobelts　(MoS2@C　NBs),　which　possess　the　nanostructure　of　MoS2　nanoflakes　completely　encapsulated　within　an　amorphous　carbon　layer,　were　obtained　by　utilizing　MoO3　nanobelts　as　self-sacrificing　templates,　followed　by　a　facile　thermal　decomposition　of　solution-evaporated　glucose　and　an　in　situ　hydrothermal　sulfidation　process.　This　unique　nanostructure　provides　not　only　good　electrical　conductivity　and　short　ion　diffusion　length,　but　also　excellent　structure　stability.　When　applied　in　lithium-ion　batteries　(LIBs)　and　sodium-ion　batteries　(NIBs),　the　nanobelts　exhibit　enhanced　electrochemical　properties.　In　LIBs,　the　nanobelts　deliver　a　high　discharge　capacity　of　1189　mA　h　g−1　after　200　cycles　at　0.2　A　g−1　and　a　long-cycle　stability　of　626　mA　h　g−1　even　after　800　cycles　under　1　A　g−1.　Furthermore,　excellent　rate　capabilities　of　1133,　1180,　1078,　926,　704　and　1249　mA　h　g−1　at　0.1,　0.2,　0.5,　1　and　0.1　A　g−1,　respectively,　are　also　acquired.　As　for　NIBs,　after　100　cycles　at　0.2　A　g−1,　a　charge　capacity　of　328.8　mA　h　g−1　can　be　maintained　and　the　retention　rate　is　83.2%.　©　2022　The　Royal　Society　of　Chemistry