VST-Floyd: a separation logic tool to verify correctness of C programs. The Verified Software Toolchain builds foundational machine-checked proofs of the functional correctness of C programs. Its program logic, Verifiable C, is a shallowly embedded higher-order separation Hoare logic which is proved sound in Coq with respect to the operational semantics of CompCert Clight. This paper introduces VST-Floyd, a verification assistant which offers a set of semiautomatic tactics helping users build functional correctness proofs for C programs using Verifiable C.