Cabo Frio is a coastal city situated in the state of Rio de Janeiro within Southeast Brazil. It occupies a distinctive geographical position where the Brazilian coastline runs east from Rio de Janeiro before turning sharply northward, placing Cabo de São Tomé to its north. The city serves as a significant tourist destination known for offering both ocean and lake beaches, attracting visitors from across the state and neighboring landlocked regions.

The city was founded in the 16th century after Portuguese forces expelled the French from the area. It remained small for most of its history before experiencing growth driven by tourism income and an influx of retirees from Rio de Janeiro. The name Cabo Frio, meaning Cold Cape, derives from the local geography and water temperatures that are colder than those in nearby cities, a characteristic attributed to the lack of mica in the white fine sand which keeps it cool in the sun.

The urban landscape features historic architecture and natural attractions that define its character. Notable heritage sites include the Sào Mateus Fort, built by the Portuguese between 1616 and 1620, and the Chapel of Nossa Senhora da Guia, constructed by Franciscans around 1740. The Church of Saint Benedict in Passagem was built in 1701 to hold mass for slaves, while the Our Lady of Assumption Church stands as another key historical building within the municipality.

Cabo Frio is a popular beach destination that draws surfers and beachgoers from around the state. The area offers diverse coastal experiences, including Fort Beach with its 7.5 kilometers of sand and Peró Beach, which is noted for surfing. The region is also a prime location for scuba diving, where southerly cold and northerly warm currents meet to create abundant marine life and visibility ranging between eight and twenty meters, with April being the best time for such activities.

As of 2025, Cabo Frio has an estimated population of 238,438 residents across its 410 square kilometers. The city is served by Cabo Frio International Airport, facilitating access for travelers. The demographic profile includes a mix of whites, mixed-race individuals, and other ethnic groups, with religious affiliations spanning evangelicals, Roman Catholics, and non-religious populations, reflecting the diverse social fabric of this growing coastal municipality.