The Delaware Naturalist Handbook is the primary public face of a major university-led public educational outreach and community engagement initiative. This statewide master naturalist certification program is designed to train hundreds of citizen scientists, K-12 environmental educators, ecological restoration volunteers, and habitat managers each year. The initiative is conducted in collaboration with multiple disciplines at the University of Delaware, the University of Delaware Cooperative Extension, the Delaware Environmental Institute (DENIN), the state Department of Natural Resources and Environmental Conservation (DNREC), the state Division of Parks, the state Forest Service, the state Division of Fish and Wildlife, and local nonprofit educational institutions, including the Mount Cuba Center, the Delaware Nature Society and Ashland Nature Center, Delaware Wildlands, Northeast Climate Hub, Center for Inland Bays, and White Clay Creek State Park. Published by University of Delaware Press. Distributed worldwide by Rutgers University Press.