John D. MacArthur Beach State Park, Nature reserve on barrier island in Palm Beach County, Florida, US.

John D. MacArthur Beach State Park covers 438 acres of land and water on and just north of Singer Island in North Palm Beach. A 1,600-foot boardwalk crosses an estuary, and the park also takes in Munyon Island in the Intracoastal Waterway. Its pale sand beach runs along a straight Atlantic shoreline, with seaweed patches and small breaking waves at the water's edge.

The land became a state park in 1989 to protect vital nesting and resting grounds for endangered sea turtles and native plant species. This preservation effort grew from increasing recognition of how valuable Florida's coastal landscapes are for wildlife survival.

The Nature Center reflects how locals and visitors connect with this coastal landscape through observation and learning about what lives here. It shows the importance of this place for understanding the balance between beach, water, and forest in the region.

The park is open from early morning until sunset and offers swimming areas, trails for walking, and places to rent kayaks. Picnic tables and restroom facilities are spread throughout the grounds, making it easy to spend a full day exploring at your own pace.

MacArthur Beach is a nesting ground for the threatened loggerhead, the endangered green sea turtle and occasionally the rare leatherback. The park's William T. Kirby Nature Center keeps two live loggerhead sea turtles on exhibit, and a local group, Friends of MacArthur Beach State Park, raises community support for the park alongside state funds and gate fees.