Tonto Natural Bridge State Park, Natural travertine bridge park in Gila County, United States.

Tonto Natural Bridge is a travertine arch, believed to be the largest natural travertine bridge in the world, spanning a 400-foot-long (120 m) tunnel that is 150 feet (46 m) wide at its widest point and 183 feet (56 m) high. The park lies off State Route 87, ten miles (16 km) north of Payson, Arizona, in Gila County. Trails such as the Pine Creek, Waterfall and Gowan trails lead to viewpoints of the arch and the creek below.

David Gowan, a Scotsman, first documented the bridge in 1877 while hiding from Apache raiders; he then tried to claim the land under squatter's rights and persuaded his family to emigrate. Gowan family members lived near the bridge until 1948, and their lodge building is listed on the National Register of Historic Places. In 1948 Glen L. Randall of Pine, Arizona, bought the bridge and the lodge with 160 surrounding acres; after his death in 1967 his widow Eloise Kleinman Randall sold the property, which eventually became a state park.

The Gowan family lived by the bridge until 1948, and their lodge still stands, listed on the National Register of Historic Places. The park is named for the Tonto, and the bridge itself takes its name from the Tonto Basin. The lodge building is the surviving trace of the family that settled here after David Gowan documented the arch in 1877.

The park has four hiking trails with varying difficulty levels, all clearly marked and accessible from the visitor center. Wear sturdy shoes and bring plenty of water, as some paths are steep and shaded, offering protection from the sun during hot seasons.

The bridge is made of travertine, a limestone deposited by calcium-rich springs, not volcanic rock. David Gowan hid beneath the arch for three days while evading Apache pursuers in 1877, and the Gowan family stayed until 1948. The park was created in 1991 and covers 65 hectares at an average elevation of 1,371 m.