Ilha do cabo Frio Biological Reserve (Portuguese: Reserva Biológica da Ilha do Cabo Frio) is a municipal biological reserve in the state of Rio de Janeiro, Brazil.

The reserve is located on an Atlantic island in the south east of the municipality of Arraial do Cabo, Rio de Janeiro.

[1] The upwelling of cold waters of the Malvinas Current near the island creates a seasonal semi-arid micro-climate and provides the conditions for dunes, hyper-saline lagoons and several endemic and unique communities of vegetation.

It has been called the "Plant Diversity Center of Cabo Frio" and recognized by the World Wildlife Fund and International Union for Conservation of Nature.

[4] The objective of the reserve is to provide full conservation of biota and other natural attributes without direct human interference, and there are restrictions to visits by the public and visits for the purpose of scientific research.