The Internal Oblique Muscle is a key muscle located in the abdomen, lying beneath the external oblique muscle. It plays a crucial role in trunk rotation and lateral flexion, helping to stabilize the core during various movements. This muscle originates from the iliac crest and the thoracolumbar fascia, and it inserts into the lower ribs and the linea alba. Functionally, the internal oblique works in conjunction with other abdominal muscles, such as the rectus abdominis and transverse abdominis, to support posture and protect internal organs. Strengthening this muscle can enhance athletic performance and improve overall core stability.