Warm Mineral Springs, Natural warm spring and archaeological site in North Port, Florida

Warm Mineral Springs is a water-filled sinkhole in North Port, Florida, formed about 30,000 years ago when a cavern roof in carbonate rock collapsed. Its circular opening is 72 metres across at the present water level, and the shaft narrows to 48 metres a few metres down before widening again toward a 70-metre-deep bottom. A spring vent 63 metres below the surface discharges warm mineralized water at roughly 30 °C.

In the late 1950s, William Royal and other scuba divers found artifacts and human bones from at least seven individuals in the sinkhole. A partially burned log found with some of the bones was radiocarbon dated to about 10,000 years ago. The site was added to the National Register of Historic Places on November 28, 1977, and the Spa Building, Cyclorama and attached sales building were listed in 2019 as the Warm Mineral Springs Building Complex.

The name refers to the consistently warm waters that have drawn bathers for generations. The facility along the shore serves today as a recreational spot, while the spring itself continues to release water naturally from deep underground.

Warm Mineral Springs lies in North Port, Florida, about a mile north of U.S. 41. The sinkhole opening is roughly 72 metres (236 ft) across at the water line, and the water stays near 30 °C (86 °F) year-round. Swimming resumed in 2014 after the site's spa era ended in 2000.

A skull recovered about 12 metres below the water surface held organic matter that hospital staff likened to brain tissue; tests were consistent with brain matter, though no cellular structure could be seen. Divers William Royal and others also raised bones of at least seven people and a partly burned log dated to roughly 10,000 years ago.