We have developed a glycosyl radical-based synthesis of C-alkyl glycosides through a deoxygenative Giese addition-reduction-cyclization cascade, in which readily available 1-hydroxy carbohydrates serve as precursors for glycosyl radicals and aryl alkenes function as radical acceptors. This reaction not only provides an effective method for accessing a previously underexplored class of functionalized cyclopropanes but also enhances the application of Giese addition in the synthesis of C-alkyl glycosides by derivatizing the radical intermediate generated through polar cyclization to yield a cyclopropane.