The South-West of Algeria exhibits rich floristic diversity, with many medicinal plants deeply rooted into the healthcare practices of the local population. While ethnobotanical knowledge is important, there are still gaps in the data regarding the use of certain species, such as Ononis angustissima. This study presents the first ethnobotanical survey focused on Ononis angustissima conducted in the provinces of Saida, Namaa, El Bayadh, and Bechar. The primary objective was to document and preserve indigenous knowledge regarding the folk usage of this plant. In this study, semi-structured questionnaires were administered to 172 inhabitants and the collected data were analyzed statistically. Quantitative analysis revealed that the majority of respondents were a married herbalist man (87.2%), mostly older and with limited education including middle school (49.07%). The high frequently treated condition was metabolic disorders, particularly hypercholesterolemia (31.1%), using the dried (62.13%) aerial parts (57.73%), typically prepared as a decoction (75.6%) and administered orally (93.26%). These findings serve as a valuable resource for scientific research and could enrich both national and global pharmacopoeias.