Lanthanide　(Ln3+)-doped　near　infrared　(NIR)-II　luminescent　nanoprobes　have　shown　great　promise　in　many　technological　fields,　but　are　currently　limited　by　the　low　absorption　efficiency　of　Ln3+　due　to　the　forbidden　4f→4f　transition.　Herein,　we　report　a　novel　NIR-II　luminescent　nanoprobe　based　on　efficient　energy　transfer　from　Ce3+　to　Er3+　and　Nd3+　in　sub-10　nm　SrS　nanocrystals　(NCs),　which　are　excitable　by　using　a　commercial　blue　light-emitting　diode　(LED).　Through　sensitization　by　the　allowed　4f→5d　transition　of　Ce3+,　the　NCs　exhibit　strong　NIR-II　luminescence　from　Er3+　and　Nd3+　with　quantum　yields　of　2.9%　and　2.3%,　respectively.　Furthermore,　by　utilizing　the　intense　NIR-II　luminescence　of　Er3+　from　the　thermally　coupled　Stark　sublevels　of　4I13/2,　we　demonstrate　the　application　of　SrS:Ce3+/Er3+　NCs　as　blue-LED-excitable　NIR-II　luminescent　nanoprobes　for　ratiometric　thermal　sensing.　These　findings　reveal　the　unique　advantages　of　SrS:Ln3+　NCs　in　NIR-II　luminescence,　which　may　open　up　a　new　avenue　for　exploring　novel　and　versatile　luminescent　nanoprobes　based　on　Ln3+-doped　sulphide　NCs.　[Figure　not　available:　see　fulltext.]　©　2021,　Science　China　Press　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.