Effective management of the growing threat of environmentalEnvironmental contaminationContamination requires monitoringMonitoring technologiesTechnology that surpass the inefficiencies of traditional laboratory techniques, which are typically resource-intensive and slow to yield results. This chapter presents biosensorsBiosensor as a viable and innovative solutionSolutions for immediate, on-site environmental assessment. At its core, a biosensor is a compact analytical tool that fuses a highly selective biological component, known as a bioreceptor, with a physical signal transducerTransducer. The present chapter will review the principal classes of biosensors, categorized by their transducersTransducer, explaining their core working mechanism. The chapter further explores a broad spectrum of applications, from identifying pesticides and heavy metalsHeavy metals to detecting pathogens and harmful organic compounds across various environmental media like waterWater, air, and soilSoil. By highlighting their critical benefits—including excellent detection limitsDetection limits, fast analysis times, portability for fieldwork, and affordability—this chapter serves as an introductory framework. It demonstrates the immense potential of biosensorsBiosensor and the futuristic aspects to transform the field of environmental pollutantPollutants monitoringMonitoring and support a more robust and sustainable approach to global environmentalEnvironmental stewardship.