This thesis provides significant insight into our understanding of river function in highly seasonal systems. In north Australia’s vast wet/dry tropics, large rivers and associated wetlands are regarded among the continent’s most biologically diverse and ecologically healthy. Until recently however, research on the hydrology, biodiversity and function of Australian rivers has focussed on the south. My thesis investigates floodplain river function in Australia’s wet/dry tropics, more specifically in the Gulf of Carpentaria drainage division, and is the first to present a dynamic conceptual model of river function for these systems. Three major themes reside within riverine ecology: flow, pattern and process. These themes feature within existing conceptual models of large river function, for example, the River Continuum Concept, the Flood Pulse Concept and the Riverine Productivity Model. These themes and models were used as a template to explore river function in the study region: flow, as broad-scale hydrology and more localised hydrological connectivity; patterns, as spatiotemporal variation in aquatic macroinvertebrate biodiversity; and processes, as organic carbon flow through aquatic macroinvertebrate food webs. The flow regime is major driver of river function, and as such, a multivariate analysis of daily flow data from large, Gulf of Carpentaria rivers was conducted. Two major classes of river were found, each with a distinct flow regime type: ‘tropical’ rivers were characterised by flow regularity and permanent hydrological connection, ‘dryland’ rivers by high levels of flow variability and ephemerality, similar to rivers in Australia’s central and semi-arid zones. However, both river types experienced seasonal change, associated with higher flow magnitudes in the wet and lower flow magnitudes in the dry, with ‘dryland’ rivers typified by greater numbers of zero flow days. These features—flow regularity and permanence for ‘tropical’ rivers, flow variability and absence for ‘dryland’ rivers, and wet/dry seasonality for both river types—were proposed as the broad-scale hydrological drivers of river function in the Gulf region and are expected to be found as important drivers throughout the wet/dry tropics.