Açude Caldeirão is a reservoir located in the municipality of Piripiri, in the state of Piauí, Brazil, at coordinates 4°21′27.5″S, 41°42′9″W. The reservoir was inaugurated in 1945 with the original purpose of regulating the flow of Rio Caldeirão. It covers approximately 0.1 square miles, making it a compact water body suited to shorter outings rather than extended touring.

Access to the reservoir is via Rodovia Artur Gonçalves de Sousa, a paved asphalt road in good condition. This road serves as the primary route for visitors arriving by vehicle.

The reservoir is recognized as the top-rated attraction in Piripiri, holding a 4.5 out of 5 rating based on 30 reviews on TripAdvisor. Visitors consistently describe it in positive aesthetic terms. Swimming is a common activity at the site, suggesting that water contact is generally considered acceptable by locals and visitors alike. Fishing is also practiced on the reservoir, with nearby waters in the region known to hold species such as fat snook and trahira.

Given its location in the semi-arid interior of Piauí, water levels are influenced by seasonal rainfall patterns, and the reservoir overflows ("sangrar") during particularly wet periods, typically around January. Paddlers planning a visit should account for the region's hot climate, with daytime temperatures frequently reaching into the low-to-mid 30s Celsius, making early morning outings preferable for comfort.

No specific paddling restrictions, designated launch ramps, or formal paddling infrastructure exist for this reservoir.