Polymer　matrix　composites　with　excellent　thermal　management　performance　have　emerged　as　remarkable　materials　in　the　realms　of　microelectronic　devices　and　wireless　communication　technologies.　However,　achieving　high　thermal　conductivity　in　most　composites　often　requires　a　high　filling　load,　which　will　compromise　other　desirable　properties.　Herein,　utilizing　physical　foaming　and　vacuum　infiltration　methods,　we　introduce　a　3D　honeycomb　composite　consisting　of　surface-hydroxylated　hexagonal　boron　nitride　(OH-BN)　and　epoxy.　The　3D　OH-BN　honeycomb　foam　in　the　composite　features　a　lightweight　design　(0.33　g/cm3),　high　strength　(7178　times　its　own　weight)　and　prominent　heat　transfer　performance.　Significantly,　these　composites　achieve　notable　thermal　properties,　including　high　through-plane　thermal　conductivity　(2.073　W　m−1　K−1)　and　relatively　low　thermal　resistance　(0.995　°C/W)　at　a　reduced　filling　load　(17.2　vol%).　In　comparison　with　pure　epoxy,　the　through-plane　thermal　conductivity　is　enhanced　by　an　impressive　894　%,　while　the　thermal　resistance　is　reduced　to　1/9.4　of　that　observed　in　pure　epoxy.　Besides,　the　3D　honeycomb　composites　combine　outstanding　mechanical　performance,　low　dielectric　properties　and　excellent　insulation,　underscoring　their　potential　in　the　field　of　thermal　management　applications　in　microelectronic　devices,　wireless　communication　systems　and　integrated　circuits.　©　2024