This article introduces the concept of S -semiprime submodules which are a generalization of semiprime submodules and S -prime submodules. Let M be a nonzero unital R-module, where R is a commutative ring with a nonzero identity. Suppose that S is a multiplicatively closed subset of R . A submodule P of M is said to be an S -semiprime submodule if there exists a fixed s ∈ S , and whenever r n m ∈ P for some r ∈ R , m ∈ M , and n ∈ ℕ , then srm ∈ P . Also, M is said to be an S -reduced module if there exists (fixed) s ∈ S , and whenever r n m = 0 for some r ∈ R , m ∈ M , and n ∈ ℕ , then srm = 0 . In addition, to give many examples and characterizations of S -semiprime submodules and S -reduced modules, we characterize a certain class of semiprime submodules and reduced modules in terms of these concepts.