The Cities Programme facilitates collaboration between government, business, and civil society to enhance sustainability in cities facing complex challenges. It is part of the UN Global Compact, the largest corporate social responsibility initiative. The Cities Programme supports over 30 signatory cities through expertise, tools, and networking. The case study of Milwaukee, USA showed how it tackled water sustainability issues through a multi-sector partnership between government, businesses like the Milwaukee Water Council, and civil society groups like Discovery World. This collaborative approach addressed economic, ecological, social, cultural, and political sustainability domains to make Milwaukee a world water hub.