Fiber-shaped　supercapacitor　(FSSC)　is　considered　as　a　promising　energy　storage　device　for　wearable　electronics　due　to　its　high　power　density　and　outstanding　safety.　However,　it　is　still　a　great　challenge　to　simultaneously　achieve　high　specific　capacitance　especially　at　rapid　charging/discharging　rate　and　long-term　cycling　stability　of　fiber　electrode　in　FSSC　for　practical　application.　Here,　a　ternary　poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/reduced　graphene　oxide/polypyrrole　(PEDOT:PSS/rGO/PPy)　fiber　electrode　was　constructed　by　in　situ　chemical　polymerization　of　pyrrole　on　hydrothermally-assembled　and　acid-treated　PEDOT:PSS/rGO　(PG)　hybrid　hydrogel　fiber.　In　this　case,　the　porous　PG　hybrid　fiber　framework　possesses　combined　advantages　of　highly-conductive　PEDOT　and　flexible　two-dimensional　(2D)　small-sized　rGO　sheets,　which　provides　large　surface　area　for　the　deposition　of　high-pseudocapacitance　PPy,　multiscale　electrons/ions　transport　channels　for　the　efficient　utilization　of　active　sites,　and　buffering　layers　to　accommodate　the　structure　change　during　electrochemical　process.　Attributed　to　the　synergy,　as-obtained　ternary　fiber　electrode　presents　ultrahigh　volumetric/areal　specific　capacitance　(389　F　cm−3　at　1　A　cm−3　or　983　mF　cm−2　at　2.5　mA　cm−2)　and　outstanding　rate　performance　(56　%,　1–20　A　cm−3).　In　addition,　80　%　preservation　of　initial　capacitance　after　8000　cycles　for　the　corresponding　FSSC　also　illustrates　its　greatly　improved　cycle　stability　compared　with　64　%　of　binary　PEDOT:PSS/PPy　based　counterpart.　Accordingly,　here　proposed　strategy　promises　a　new　opportunity　to　develop　high-activity　and　durable　electrode　materials　with　potential　applications　in　supercapacitor　and　beyond.　©　2023　Elsevier　Inc.