ABSTRACT: Metathesis and reversible catalytic reactions are fundamentally intriguing and powerful tools in modern synthetic chemistry. While most reversible catalytic reactions are predicated on breaking and forming reactive functional groups, the ability to leverage the C-H bond as a functional group into metathesis reactions has proved to be exceptionally challenging. Here, we develop a C-H/C-X metathesis reaction through a radical swapping protocol where a hydrogen and halogen are traded between molecules via reversible hydrogen atom transfer (HAT) and halogen atom transfer (XAT) that allows for mild C-H halogenation. The reversibility of this process allows for selective dehalogenation of polyhalogenated products to form monohalogenated products. Leveraging the reversibility of this process, halogenated organic pollutants can also serve as a halogen source for C-H halogenation. In the broader context, this work establishes that incorporating reversible metathesis logic in C-H bond functionalization can provide complementary advantages in synthetic strategies.