This is the first in a planned series of articles about the breeding behaviour of Brazilian birds. Field work has been carried out in various regions of Brazil since the 1980s. The descriptions cover various aspects of reproductive biology, such as seasonality, nest architecture, materials and measurements, clutch size, egg colour, size and shape, incubation period, nestling period, and parental care. Many data are presented scientifically for the first time. In this first paper, we present data for 16 species: Greater Rhea Rhea americana (two nests, including the first information from north-east Brazil), Small-billed Tinamou Crypturellus parvirostris (20 nests), Red-winged Tinamou Rhynchotus rufescens (three nests), Spotted Nothura Nothura maculosa (11 nests), Horned Screamer Anhima cornuta (four nests, possibly with the first biometrics of eggs in the wild from Brazil), Southern Screamer Chauna torquata (five nests), White-faced Whistling Duck Dendrocygna viduata (three nests), Black-bellied Whistling Duck D. autumnalis (eight nests), Muscovy Duck Cairina moschata (two nests), Brazilian Teal Amazonetta brasiliensis (one nest), White-cheeked Pintail Anas bahamensis (one nest), Rusty-margined Guan Penelope superciliaris (seven nests, probably with the first data on reproductive success), Chaco Chachalaca Ortalis canicollis (one nest), East Brazilian Chachalaca O. araucuan (one nest), Least Grebe Tachybaptus dominicus (six nests) and Pied-billed Grebe Podilymbus podiceps (one nest).