The Four Rivers Project (4RP) is a vast river diversion and restoration project in South Korea, including four major river systems and 14 tributaries over 634 km. Carried out in 2009-11 under former President Lee Myung-bak, the project faced lawsuits and protests from different stakeholders throughout the whole process. The project aimed to secure water resources, enable flood control, improve water quality and restore ecosystems. Through collusion and kickbacks, however, powerful South Korean business groups and politicians, including President Lee, benefitted from the project, while experts and communities were excluded from decision-making. This inflated the project's costs and resulted in substandard construction that worsened the water quality and still requires excessive maintenance costs. Transparency International Korea is now supporting CSOs, communities and experts pursuing project restoration and accountability from those responsible for the damage. The 4RP shows the need for meaningful prior consultation, collaboration with different stakeholders and strong oversight during planning and construction.