This chapter aims to provide a comprehensive review of the various pretreatment methods applied to biomass waste. These procedures are critical for enhancing the efficiency and effectiveness of converting biomass waste into energy or high-value-added products. The discussion will cover physical, chemical and biological pretreatment techniques. Each technique offers unique advantages and challenges, depending on the type of biomass, the application and economic and environmental factors. In this chapter, we present an overview of these pretreatment methods, highlighting their role in improving treatment efficiency, product yield and the overall sustainability of biomass treatment processes.