Waterkeeper Alliance is a global environmental network founded in 1999, uniting over 300 local Waterkeeper organizations dedicated to protecting clean water in communities around the world. The organization originated from the grassroots Waterkeeper movement that began in 1966 on New York’s Hudson River, driven by efforts to combat industrial pollution and restore the river's health. Headquartered in Manhattan, New York, it was co-founded by Robert F. Kennedy Jr.

The Alliance serves as a coordinating body for independent Waterkeeper groups that share a mission to defend the right to drinkable, fishable, and swimmable water. It supports these groups through environmental advocacy, community engagement, and legal enforcement. Waterkeeper organizations monitor local waterways, educate the public, and use litigation to challenge polluters. The Alliance connects and supports Waterkeeper organizations globally, facilitating knowledge sharing and amplifying their collective impact, ultimately advocating for nearly one billion people's access to clean and safe water.