[Truncated abstract] The southern-temperate spider family Micropholcommatidae is a poorly-studied taxon of uncertain limits and uncertain affinities. Since the first Australian species were described in the early twentieth century, and the family was erected in 1944, the taxonomic status and phylogenetic placement of the Micropholcommatidae have been the subject of ongoing debate. Various phylogenetic hypotheses have been proposed for the family, but these hypotheses have never been tested with a robust phylogenetic analysis – a problem compounded by the inadequate state and confusing history of micropholcommatid taxonomy. To address the many gaps in our understanding of micropholcommatid interrelationships, this thesis will present a comprehensive systematic treatment of the family. Using a combination of molecular phylogenetic, morphological cladistic and taxonomic methods, micropholcommatid diversity is documented and tested at multiple systematic levels, with an alpha-taxonomic and biogeographic focus on the diverse Australian fauna. The taxonomic contribution is substantial throughout, with one new family, two new subfamilies, one new tribe, 14 new genera and 37 new species described. A combined molecular phylogenetic study is presented in Chapter 2, as a 'first pass' exploration of the monophyly, limits and phylogenetic position of the family Micropholcommatidae. The analyses incorporated 50 ingroup spider species, including 23 micropholcommatid taxa, with nucleotide sequences obtained from two nuclear ribosomal RNA genes (18S and 28S). ...The new subfamily Gigiellinae is also described for two enigmatic species in the newly-described genus Gigiella, known only from the temperate Nothofagus rainforests of south-eastern Australia and southern Chile. As a final contribution to micropholcommatid taxonomy, and as an extension to the cladistic analyses presented in Chapter 5, the new spider family Teutoniellidae is proposed in Chapter 6 for three genera from South America, South Africa and Australia. Teutoniellid monophyly is evidenced by at least two unambiguous synapomorphies, and the morphology of the family is described in relation to other symphytognathidan and EbCY spider taxa. The nominate genus Teutoniella is redescribed to include three species from South America, along with an additional new species from Tasmania. Two new teutoniellid genera are also described, each for a single new species from South Africa: Inflaticrus ansieae is described from the Langeberg Range, east of Cape Town; and Woldius hennigi is described from near Pietermaritzburg, north-west of Durban. In summary, this thesis provides a taxonomic and phylogenetic framework for all future research on micropholcommatid spiders. It presents new data on the phylogeny, phylogenetic position, composition, biogeography, molecular evolution and natural history of a previously poorly-known group of spiders, and highlights a number of remaining gaps in our knowledge of micropholcommatid and araneoid systematics. As a novel contribution to scholarship, this thesis synthesises taxonomic and phylogenetic hypotheses at multiple systematic levels, and tests those hypotheses with original, combined datasets.