This chapter focuses on the plasmonic sensors in various applications. It describes their market potential, their underlying theory of operation, the nature of the plasmonic field enhancements responsible for the sensory response, the selection of materials and structures, and a model fabrication example for achieving desired plasmonic structures. Plasmonics has showed an inspiring potential in any application where the confinement and manipulation of electromagnetic fields play a role, making use of the advantages of photonics at the miniaturized size range of the electronics. The rapid development of modern plasmonics has benefited significantly from top-down microelectronics fabrication methods, and microelectronics fabrication materials and strategies remain indispensable for the development of state-of-the-art plasmonic sensors. Optimizing the requirements for efficient hot-electron generation at plasmonic metal–dielectric interfaces is thus a key element in the development of efficient plasmonic photovoltaics as well as low-power plasmonic sensors.