Heteroarenes are a ubiquitous structural motif of new pharmaceuticals, agrochemicals, and functional materials. Thus, the development of methods for the synthesis of structurally diverse heteroarenes represents an important objective in organic synthesis. We have developed Pd-catalyzed C−H alkenylation reactions of five-membered heteroarenes. Electronic characters of palladium catalytic systems were manipulated to achieve regioselective C−H alkenylation of nitrogen-containing five-membered heteroarenes, such as pyrazoles, imidazoles, and pyrroles. Readily available acrylates, acryl amides, and styrene derivatives were employed as alkenyl group donors in these C−C bond forming reactions to provide alkenyl heteroarenes with desired substitution patterns. Furthermore, a benzannulation strategy involving subsequent alkenylation followed by oxidative cyclization was developed to afford fused heteroarene rings. This approach based on C−H functionalization complements other cyclization methods and allows the systematic preparation of new, highly functionalized heterocyclic compounds.