Foamed　lightweight　soil　(FLS)　is　frequently　used　for　roadbed　backfilling;　however,　excessive　cement　use　contributes　to　higher　costs　and　energy　consumption.　Desulfurized　gypsum　(DG),　a　by-product　of　industrial　processing　with　a　chemical　composition　similar　to　natural　gypsum,　presents　a　viable　alternative　to　cement.　This　study　evaluates　the　potential　of　DG　to　replace　cement　in　FLS,　creating　a　new　material,　desulfurized　gypsum　foamed　lightweight　soil　(DG-FLS).　This　article　is　conducted　on　DG-FLS　with　varying　DG　content　(0–30%)　to　assess　its　flowability,　water　absorption,　unconfined　compressive　strength　(UCS),　durability,　and　morphological　characteristics,　with　a　focus　on　its　suitability　for　roadbed　backfilling,　though　its　performance　over　the　long　term　in　engineering　applications　was　not　evaluated.　Results　show　that　as　DG　content　increased,　flowability,　water　absorption,　and　UCS　decreased,　with　values　falling　within　the　range　of　175–183 mm,　8.24–12.49%,　and　0.75–2.75 MPa,　respectively,　all　of　which　meet　embankment　requirements.　The　inclusion　of　DG　enhanced　the　material’s　plasticity,　improving　failure　modes　and　broadening　its　applicability.　Durability　tests　under　wet-dry　and　freeze–thaw　cycles　showed　comparable　performance　to　traditional　FLS,　with　UCS　exceeding　0.3 MPa.　Additionally,　the　incorporation　of　SO42−　in　DG-FLS　reduced　sulfate　diffusion,　decreased　C–S–H　content,　and　increased　calcium　sulfate　content,　improving　sulfate　resistance.　After　120 days　of　exposure　to　sulfates,　the　durability　coefficient　of　DG-FLS　surpassed　100%,　with　a　25%　improvement　over　traditional　FLS.　A　sustainability　analysis　revealed　that　DG-FLS　not　only　meets　engineering　strength　requirements　but　also　offers　economic　and　environmental　benefits.　Notably,　DG-12　showed　a　20%　reduction　in　environmental　impact　compared　to　conventional　FLS,　underscoring　its　potential　for　more　sustainable　construction.　©　King　Fahd　University　of　Petroleum　&　Minerals　2025.