Ribeirão Mestre-d'Armas is a tributary stream flowing through the Federal District of Brazil, draining into the Rio São Bartolomeu within one of the largest Environmental Protection Areas (Área de Proteção Ambiental) in the Federal District. The stream winds through a landscape shaped by the Cerrado — Brazil's vast tropical savanna — and passes through a distinct environmental gradient that ranges from well-preserved headwater areas to transitional zones and, further downstream, more urbanized stretches near the municipality of Planaltina. This gradient gives the stream a varied character, with upper reaches retaining much of their ecological integrity while lower sections reflect the pressures of surrounding development. The sub-basin of Ribeirão Mestre-d'Armas sits within coordinates roughly 15°33'12" to 15°41'41" S and 47°33'16" to 47°47'15" W, placing it squarely within the central Brazilian plateau at elevations typical of the Federal District's highland Cerrado terrain.