Addressing　environmental　concerns　associated　with　conventional　fluoride-based　fire　extinguishing　foams,　this　study　proposes　the　use　of　calcined　gypsum　and　nano　silica　(NS)　to　develop　eco-friendly　lightweight　nano　gypsum　foam　(Nano　GF)　as　a　sustainable　alternative,　which　exhibits　exceptional　extinguishing　efficiency,　requiring　only　50　%　and　70　%　of　the　mass　needed　by　commercial　aqueous　film-forming　foam　(AFFF)　to　suppress　n-heptane　and　ethanol　fires,　respectively.　Calcined　gypsum　and　NS　work　synergistically　to　enhance　foam　stability,　yielding　an　impressive　half-life　of　360　min　for　Nano　GF,　double　that　of　Base　Foam　without　calcined　gypsum　or　NS.　Nano　GF　of　ρ　=　65　kg/m³　maintained　its　original　height　without　melting　when　exposed　to　the　fire　of　500　°C　for　30　s,　outperforming　the　fire　resistance　of　gypsum　foam　(GF)　of　ρ　=　85　kg/m³　without　NS.　At　120°C,　Nano　GF　demonstrates　superior　endurance,　evaporating　in　80　s,　compared　to　50　s　for　AFFF.　The　synergistic　effects　between　calcined　gypsum,　NS,　and　cetyltrimethylammonium　bromide　(CTAB)　in　enhancing　the　Nano　GF＇s　stability　and　fire　resistance　are　revealed　by　ab-initio　calculation　and　chemical　analyses.　NS　and　gypsum　stabilize　the　CTAB　foam　through　electrostatic　adsorption　and　hydrogen　bonding,　while　calcined　gypsum　acts　as　a　flame　retardant.　NS　inhibits　gypsum　agglomeration,　ensuring　larger　contact　area　between　gypsum　and　flame,　thereby　enhancing　its　fire　resistance,　while　simultaneously　reducing　foam　density　and　enhancing　the　flowability　of　the　foam　in　firefighting　scenarios.　This　research　highlights　Nano　GF＇s　potential　as　a　fluorine-free　solution　for　Class　B　fires,　paving　the　way　for　innovative　uses　of　natural　resources　in　firefighting　technology.　©　2025　Elsevier　Ltd