Methacrylic acid and its ester methylmethacrylate are two important monomers for high-performance polymer applications. In this chapter we will try to highlight pathways that use partial oxidation reactions for the synthesis of both monomers and shed some light on the current understanding of the structure–property relationships for the catalytic materials employed for the respective processes. In contrast to typical oxygenates of the C2-, C3-, C4- and C8-value chains there are a number of technical routes to methacrylic acid (MAA) that are currently employed on an industrial basis or which have been brought to a maturity that is close to commercialization. Due to the large number of approaches we will mainly focus on selected routes that are specific for partial oxidation reactions to methacrylic acid and omit catalyst systems and routes that are currently successfully employed in the C3-, C4- and C8-value chains and are considered potential candidate systems for routes to methacrylic acid as well.