Constructed wetlands (CWs) treatment systems are engineering systems designed and constructed to capitalize on the natural processes of wetland soils, plants, and the microbial communities that are associated with them. Although constructed wetlands function in controlled settings, they are structured to replicate and enhance the beneficial processes that occur naturally in wetland ecosystems. The two techniques that are most frequently utilized for (CWs) are the type of vegetation used and the direction of water flow. The two main types of CWs that are dictated by the water flow pattern over the system are free-water surface (CWs), often referred to as Surface Flow (CWs), and Subsurface Flow (CWs). The classification of Subsurface Flow (CWs) into vertical and horizontal flow systems is based on the direction of the flow stream. It can be classified upon floating treatment, submerged macrophyte wetlands, or emergent macrophyte. The type of vegetation to be included is another crucial component of CWs systems. Artificial wetlands for wastewater treatment were developed by German scientists in the 1950s. The design-based evolution and development of (CWs) globally, including present patterns and potential future directions, will be covered in this chapter. Over the past five decades, CWs have evolved to serve multiple applications, including managing stormwater runoff, treating landfill leachate, supporting energy recovery through microbial fuel cells, addressing agricultural pollution, reducing urban heat island effects, and contributing to circular economy and ecosystem resilience.