This article provides useful information on the distribution of sweet chestnut (Castanea sativa) and presents additional data on the ecology, chorology and phytocenology of the species in the Oltenia region, Romania, based on literary sources, herbaria and field observations. By providing accurate and detailed data, this study contributes significantly to the existing knowledge, as well as mapping efforts of the species at the European level. In the subspontaneous flora of the Oltenia region, the C. sativa species is found in sheltered resorts in the counties of Gorj (Glogova, Valea Perilor, Tismana, Pocruia, Polovragi, etc.) and MehedinÈi (ComÄneĆti, Baia de AramÄ, etc.), on mesobasic soils, balanced from a hydraulic point of view. The phytocenoses where this species grows are rich in southern elements (e.g., Cornus mas L., Cerasus avium (L.) Moench, Quercus dalechampii Ten., Tilia tomentosa Moench). They are included in the Castaneo-Quercetum Horvat 1938 association. In Romania, habitats that include areas occupied by sweet chestnut are classified within habitat R4141âDaco-Balkan forests of oak (Quercus petraea) and chestnut (C. sativa) with Genista tinctoria. This habitat has a very high biodiversity conservation value and ecological importance. According to the Natura 2000 directive, sweet chestnut forests are included in the habitat category 9260, which underlines the importance at the European level for biodiversity conservation.