With the expansion of urban areas and increasing distances to waste disposal sites, efficient systems for waste collection and transfer have become essential. This chapter introduces the classification, structure, principle, basic parameters, and development trends of waste compactors. First, waste compactors are categorized by installation type, compaction principle, compaction direction, compaction form, productivity, and their role in waste collection and transfer stations. Second, the main structures and principles of different compactors are discussed, including horizontal direct-compaction, horizontal precompaction, vertical, and moveable waste compactors. Third, key performance parameters such as compaction ratio, compactness, compaction force, force pressure, and capacity are detailed. Finally, the development trends of waste compactors are outlined, focusing on increased automation and intelligence, improved auxiliary and environmental facilities, more versatile layouts, and compatibility with waste sorting.