It　is　still　an　enormous　challenge　to　regulate　microstructure　of　pure　carbonaceous　electromagnetic　(EM)　wave　absorbents　in　order　to　gain　superior　wideband　microwave　absorption　(MA)　with　environmentally　adaptive　ability.　Herein,　the　novel　pure　cellulose-derived　graphite　carbon　materials　(CGC)　with　abundant　defects　were　fabricated　via　the　self-assembly　strategy　combined　with　simple　carbonization　for　the　first　time.　The　EM　and　MA　performance　of　as-prepared　CGC　with　different　carbonization　temperatures　were　studied　in　detail.　The　minimum　reflection　loss　of　CGC　was　up　to-　46.2　dB　(over　99.99%　MA)　at　only　1.42　mm,　and　the　maximum　effective　absorption　bandwidth　(EABmax,　max　,　RL　＜-　10　dB)　was　as　wide　as　6.32　GHz.　The　greatly　improved　MA　of　pure　carbon　materials　outperformed　those　of　many　previously　reported　carbon-based　composite　absorbents　with　tedious　preparation　process.　The　excellent　MA　property　was　attributed　to　the　optimal　synergy　of　good　impedance　matching　and　satisfactory　EM　attenuation　capability.　Besides,　the　CGC　still　retains　a　strong　and　broadband　MA　ability　in　the　simulated　real　harsh　environmental　conditions　(acid　rain/alkaline　solution,　salt　spray　and　strong　UV　exposure).　Hence,　the　CGC　is　believed　to　be　a　very　promising　candidate　as　high-efficiency　EM　wave　absorbents　with　wide　frequency　and　excellent　environmental　adaptability　for　practical　application.　(c)　2024　The　Authors.　Published　by　Elsevier　B.V.　on　behalf　of　The　Chinese　Ceramic　Society.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).