Nanoporous　metals　with　high　specific　surface　area,　excellent　conductivity,　and　unique　surface　structure　have　attracted　attention　in　a　variety　of　applications　such　as　catalysis,　energy　storage,　and　sensing.　However,　there　is　a　significant　challenge　for　the　fabrication　of　uniform　nanoporous　architectures　in　metals　through　a　simple　and　costeffective　process.　In　this　study,　we　report　a　facile　approach　to　create　monolithic　nanoporous　Ag　(MNPA)　from　the　direct　reduction　of　insoluble　Ag2O　precursor　in　an　aqueous　solution,　fundamentally　avoiding　the　introduction　of　secondary　components　and　complex　preparation　of　precursors.　The　formation　of　porous　structures　is　attributed　not　only　to　the　volume　shrinkage　but　also　to　the　spontaneous　reconstruction　of　reserved　Ag　atoms　during　the　reduction　process.　Furthermore,　for　a　typical　application,　the　optimized　MNPA　with　a　small　grain　size　(-113　nm)　is　used　as　a　surface-enhanced　Raman　scattering　(SERS)　substrate,　which　exhibits　ultrahigh　SERS　sensitivity　with　an　enhancement　factor　of　-109.