Australian freshwaters are home to approximately 256 fish species from 36 families, many of which are endemic to the country and considered threatened, vulnerable or rare in the wild. In part this is due to a long history of continental isolation where increasing aridity and flow unpredictability have given rise to a fish fauna characterised by a unique association of life-history traits (i.e. characteristics of an organism that contribute to its fitness or performance, and which allow it to function in the environment) in order to cope with natural variation in environmental seasonality, stability and predictability. My thesis presents an assessment of life- history traits and the functional diversity (the range and value of organismal characteristics) of Australian freshwater fish at multiple spatial scales (i.e. continental, river basin, catchment and population scales), with an emphasis on phylogenetic relationships, environmental determinants and conservation biology.