Denis Hayes (1944–) is the director of the Bullitt Foundation, established to protect, restore, and maintain the natural environment of the Pacific Northwest, and an environmental activist and policy worker whose first claim to fame was as the coordinator of the first Earth Day in 1970.

Raised in rural Washington State, Hayes attended college at Stanford University (B.A. in history) and Harvard's Kennedy School of Government and was an avid backpacker as a student, as well as a an activist involved in the antiwar effort. When Senator Gaylord Nelson (D-WI), a vocal environmentalist, reformer, and small business advocate, organized Earth Day as a teach-in modeled after the Vietnam War teach-ins of the era, he chose Hayes as the event's coordinator. Nelson's principal innovation, a change from ...