Eucalyptus perangusta, commonly known as the Fine-leaved Mallee, is a species of mallee eucalyptus native to a restricted area in Western Australia. This plant is characterized by its distinctive growth habit and foliage, which contribute to its unique ecological role and aesthetic appeal. As a mallee, it typically grows as a multi-stemmed shrub or small tree, rarely exceeding 5 meters in height. Its stems are slender and often arching, arising from a lignotuber, which is a woody swelling at the base of the stem that stores carbohydrates and allows the plant to resprout after fire or damage. The leaves of Eucalyptus perangusta are a key distinguishing feature, giving rise to its common name. They are notably fine and linear to narrowly lanceolate, measuring approximately 4-8 cm in length and only 2-5 mm in width. The adult leaves are concolorous, meaning they are the same color on both the upper and lower surfaces, and are typically a dull green. This fine, needle-like foliage is adapted to arid conditions, reducing water loss through transpiration. The juvenile leaves, if present, are similar in form but may differ slightly in color or texture. Flowering occurs from late winter to spring, producing creamy white flowers that are borne in axillary inflorescences. Each inflorescence typically contains between 7 and 11 flowers. The flower buds are obovoid and lack a distinct operculum scar, or have a very obscure scar, with the operculum being conical. The fruits are small, urceolate (urn-shaped) to globose capsules, approximately 5-7 mm long and 5-6 mm wide, containing small seeds. The bark is smooth and shedding, typically powdery and white to pale grey, peeling in long ribbons. Eucalyptus perangusta is found in the southwestern region of Western Australia, specifically in the vicinity of the Stirling Range. It thrives in sandy soils, often on slopes or in low-lying areas, and is typically found in mallee scrub or heathland vegetation communities. Its restricted distribution highlights its specialized habitat requirements. Cultivation outside its native range is not widespread, but it would likely require well-drained sandy soils and a climate with dry summers, mirroring its natural environment. This species plays a role in its local ecosystem, providing habitat and food sources for native fauna. The nectar from its flowers can attract insects and birds, while its foliage may be browsed by herbivores. While not extensively utilized for commercial purposes, like many eucalypts, its essential oils may possess aromatic properties, though specific documented uses are limited. The Fine-leaved Mallee is a testament to the diversity of Eucalyptus species adapted to the unique environmental conditions of Western Australia, with its slender form and delicate foliage making it a notable component of its native flora.