The foraminiferal fauna of Broken Bay, a complex estuary along the east coast of Australia, has been analysed. All the species found (181) have been identified and the individuals counted. From these data biotopes have been determined and their geographical extent briefly analysed in relation to the sediment distribution and the hydrological parameters. A large and varied benthonic population exists predominantly in the section of the estuary not subject to large salinity changes. Taxonomic notes on 56 species, out of 168 forming the benthonic population, are also included; two species, Haplophragmoides australensis and Cribrononion sydneyensis, are described as new taxa. An additional five species and one subspecies are recorded for the first time from Australian waters.