Pain on the left side of the stomach under the ribs may be related to gastric ulcer, costochondritis, trauma and other causes. 1. Gastric ulcers: Ulcers on the inner wall of the stomach can lead to stomach pain, which is more obvious after eating, and may appear as pain on the left side of the stomach under the ribs. 2. Costochondritis: Inflammation of the costal cartilage can cause pain in the left side of the stomach under the ribs due to irritation of the rib cage by inflammatory factors. 3. Trauma: If the area is damaged by impact or other traumatic injuries, resulting in fractures or local soft tissue damage, pain symptoms may occur. It is recommended that people with pain in the left side of the stomach against the lower ribs go to the hospital in time to clarify the cause of the disease, and carry out standardized treatment under the guidance of the doctor, so as to avoid delays in the condition.