Constructed wetlands (CWs) represent a sustainable and natural approach to wastewater treatment, utilizing ecological processes to address environmental and public health concerns. Therefore, this chapter offers a comprehensive overview of CW classification and designs, tailored to specific wastewater treatment requirements, and explores various CW configurations and their adaptability, providing a foundational understanding of their diverse roles in environmental engineering. Present chapter also provides practical guidance and best practices for achieving optimal performance and longevity. It presents an empirical assessment of the practical challenges and successes encountered in large-scale CW implementation, discussing innovative approaches and technological advancements to enhance the effectiveness and applicability of CWs. Finally, the sustainability of CWs is evaluated from environmental, economic, and social perspectives, emphasizing the integration of sustainable practices in CW design and operation to maximize their benefits for wastewater treatment and ecological conservation.