The public trust doctrine is an ancient legal principle undergoing a modern resurgence. Under it, governments hold certain natural resources in trust for the benefit of present and future generations, and have a judicially enforceable legal obligation to protect trust resources and the public’s interest in them. This Article argues that courts could use the public trust doctrine to enforce regulation of water pollution caused by pesticides because the current regulatory framework is insufficient to protect human health, the environment, wildlife, or water quality. The author also argues that the federal environmental statutes regulating pesticides do not preempt the public trust doctrine, at least when the claim is brought under state law.