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Acacia tumida has a wide natural distribution in north west Australia over a wide range of sites and environmental conditions. The species exhibits considerable geographically-based morphological variation. It ranges from a low, spreading shrub in desert areas to small tree form in wetter environments, and there is geographic variation in phyllode size, shape and colour. Eighteen seed-lots from across the natural distribution were tested in a provenance trial at Kununurra, Western Australia, to assess the extent to which morphological variation was genetically controlled. Based on growth habit and phyllode size and shape, three variants were recognised: a tree form (Variant 1); a multistemmed shrub form (Variant 2); and a narrow phyllode form (Variant 3). The variants are described and a botanical key for their identification presented. A summary of climate and soil data for the natural occurrences of the variants is given, and their significance in relation to domestication programs briefly discussed.