This lumbar support belt (1) may be fitted around the lower part of a patient's trunk; it comprises a strip (2) of elastic textile material provided at each end with means for attaching the strip to itself and at least two posterior boning elements made of an elastic material (5a, 5b) positioned one on each side of the transverse mid-plane (A) of the strip; the belt may be positioned on the patient in such a way that the ends of the strip fasten together over the abdominal region of the patient and the posterior boning elements (5a, 5b) press against the lumbar region of the patient; in addition, the posterior boning elements (5a, 5b) are arranged in a V-shape in such a way that the posterior boning elements (5a, 5b) converge towards the lumbo-sacral region of the patient.