The Great Lakes hold immense socioeconomic, environmental, and cultural value for those who live within and outside the region. They comprise the largest freshwater ecosystem on Earth, providing jobs, food, water, and recreation to millions of people and habitat to thousands of species of wildlife. However, the health of the Great Lakes ecosystem continues to be threatened by human-caused problems, including climate change, habitat loss, invasive species, and pollution. Plastic is an emerging form of pollution in the Great Lakes—researchers estimate that 22 million pounds of plastic enter the Great Lakes annually [12], and managing this plastic is proving complicated. Why? First, plastic pollution comes from many sources, both land- and water-based, and enters the natural environment from many pathways, so there is no universal solution for preventing its release. Second, plastic is a transboundary pollutant, meaning it can travel far from where it originates through the movement of air and water, so any effective action must take place at a larger, regional scale. Expanding the use of the Great Lakes Water Quality Agreement—the voluntary agreement between Canada and the United States—provides a promising mechanism to coordinate comprehensive action on plastic pollution across the entire region.