Most　previous　investigations　on　foam　concrete　have　been　confined　to　portland　cement　and　the　density　range　of　400-1,600　kg/m(3).　The　present　study　aims　to　develop　a　new　foam　concrete　with　a　density　ranging　from　250　to　400　kg/m(3)　by　replacing　portland　cement　with　magnesia　phosphate　cement　(MPC).　Extensive　laboratory　tests　were　performed　to　characterize　the　fresh　properties,　strength,　water　resistance,　and　thermal　conductivity　of　the　MPC　foam　concrete.　In　the　experimental　studies,　mixtures　were　prepared　by　replacing　fine　sand　with　various　contents　of　fly　ash.　The　results　show　that　an　appropriate　workability　value　is　achieved　at　a　water-solid　ratio　of　0.30,　at　which　a　foam　concrete　mixture　with　a　good　stability　and　consistency　can　be　produced.　Using　fly　ash　to　replace　fine　sand　can　improve　the　properties　of　MPC　foam　concrete,　includings　its　compressive　strength,　water　resistance,　and　thermal　conductivity.　Novel　super-lightweight　foam　concretes　with　dry　densities　ranging　from　210　to　380　kg/m(3)　were　produced,　with　strengths　ranging　from　1.0　to　2.8　MPa　and　thermal　conductivities　ranging　from　0.049　to　0.070　W/m　.　K.　(C)　2014　American　Society　of　Civil　Engineers.